Wireless communication method and wireless communication terminal, which use discontinuous channel

ABSTRACT

The present invention relates to a wireless communication method and a wireless communication terminal using a non-contiguous channel. To this end, provided are a wireless communication terminal including a processor and a transceiver, wherein the processor receives a wireless packet through the communication unit, obtains total bandwidth information indicated via a bandwidth field of HE-SIG-A of the received packet, obtains information of an unassigned resource unit via at least one of the bandwidth field of the HE-SIG-A and a subfield of HE-SIG-B of the received packet, and decodes the received packet based on the total bandwidth information and the information of the unassigned resource unit and a wireless communication method using the same.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal which use non-contiguous channel, andmore particularly, to a wireless communication method and a wirelesscommunication terminal for efficiently signaling non-contiguous channelallocation information.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelessLAN technology that can provide a rapid wireless Internet service to themobile apparatuses has been significantly spotlighted. The wireless LANtechnology allows mobile apparatuses including a smart phone, a smartpad, a laptop computer, a portable multimedia player, an embeddedapparatus, and the like to wirelessly access the Internet in home or acompany or a specific service providing area based on a wirelesscommunication technology in a short range.

Institute of Electrical and Electronics Engineers (IEEE) 802.11 hascommercialized or developed various technological standards since aninitial wireless LAN technology is supported using frequencies of 2.4GHz. First, the IEEE 802.11b supports a communication speed of a maximumof 11 Mbps while using frequencies of a 2.4 GHz band. IEEE 802.11a whichis commercialized after the IEEE 802.11b uses frequencies of not the 2.4GHz band but a 5 GHz band to reduce an influence by interference ascompared with the frequencies of the 2.4 GHz band which aresignificantly congested and improves the communication speed up to amaximum of 54 Mbps by using an OFDM technology. However, the IEEE802.11a has a disadvantage in that a communication distance is shorterthan the IEEE 802.11b. In addition, IEEE 802.11g uses the frequencies ofthe 2.4 GHz band similarly to the IEEE 802.11b to implement thecommunication speed of a maximum of 54 Mbps and satisfies backwardcompatibility to significantly come into the spotlight and further, issuperior to the IEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of awireless interface accepted by 802.11n, such as a wider wirelessfrequency bandwidth (a maximum of 160 MHz), more MIMO spatial streams (amaximum of 8), multi-user MIMO, and high-density modulation (a maximumof 256 QAM). Further, as a scheme that transmits data by using a 60 GHzband instead of the existing 2.4 GHz/5 GHz, IEEE 802.11ad has beenprovided. The IEEE 802.11ad is a transmission standard that provides aspeed of a maximum of 7 Gbps by using a beamforming technology and issuitable for high bit rate moving picture streaming such as massive dataor non-compression HD video. However, since it is difficult for the 60GHz frequency band to pass through an obstacle, it is disadvantageous inthat the 60 GHz frequency band can be used only among devices in ashort-distance space.

Meanwhile, in recent years, as next-generation wireless LAN standardsafter the 802.11ac and 802.11ad, discussion for providing ahigh-efficiency and high-performance wireless LAN communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless LAN environment, communication havinghigh frequency efficiency needs to be provided indoors/outdoors underthe presence of high-density stations and access points (APs) andvarious technologies for implementing the communication are required.

DISCLOSURE Technical Problem

The present invention has an object to providehigh-efficiency/high-performance wireless LAN communication in ahigh-density environment as described above.

Technical Solution

In order to achieve the objects, the present invention provides awireless communication method and a wireless communication terminal asbelow.

First, an exemplary embodiment of the present invention provides awireless communication terminal, the terminal including: a processor;and a communication unit, wherein the processor receives a wirelesspacket through the communication unit, obtains non-contiguous channelallocation information of the received packet, and decodes the receivedpacket based on the obtained non-contiguous channel allocationinformation.

In addition, an exemplary embodiment of the present invention provides awireless communication method of a wireless communication terminal,including: receiving a wireless packet; obtaining non-contiguous channelallocation information of the received packet; and decoding the receivedpacket based on the obtained non-contiguous channel allocationinformation.

Another exemplary embodiment of the present invention provides a basewireless communication terminal, the terminal including: a processor;and a communication unit, wherein the processor performs a CCA ofmultiple channels for a wideband packet transmission, and transmits apacket through at least one channel which is idle based on a result ofperforming the CCA of multiple channels, wherein when the packet istransmitted through a non-contiguous channel, the processor signalsnon-contiguous channel allocation information via a non-legacy preambleof the packet.

In addition, another exemplary embodiment of the present inventionprovides a wireless communication method of a base wirelesscommunication terminal, including: performing a CCA of multiple channelsfor a wideband packet transmission, and transmitting a packet through atleast one channel which is idle based on a result of performing the CCAof multiple channels, wherein when the packet is transmitted through anon-contiguous channel, non-contiguous channel allocation information issignaled via a non-legacy preamble of the packet.

The non-contiguous channel allocation information may be indicated viaat least one of a subfield of HE-SIG-A and a subfield of HE-SIG-B of thereceived packet.

The non-contiguous channel allocation information may indicateunassigned channel information in units of 20 MHz.

The non-contiguous channel allocation information may be indicated via abandwidth field of the HE-SIG-A, and the bandwidth field may indicatetotal bandwidth information through which the packet is transmitted, andchannel information to be punctured within the total bandwidth.

The bandwidth field may index puncturing of a secondary 20 MHz channeland puncturing of at least one of two 20 MHz channels in a secondary 40MHz channel, respectively.

The non-contiguous channel allocation information may be indicatedthrough a predetermined index of a resource unit allocation field of theHE-SIG-B.

The resource unit allocation field may indicate a specific resource unit(RU) not assigned to a user through a predetermined index.

The specific resource unit not assigned to a user may be at least one ofa 242-tone resource unit, a 484-tone resource unit, and a 996-toneresource unit.

The non-contiguous channel allocation information may be obtainedthrough resource unit arrangement information indicated by the resourceunit allocation field of the HE-SIG-B and a Null STA ID contained in auser field corresponding to a specific resource unit in the resourceunit arrangement.

The specific resource unit may be at least one of a 26-tone resourceunit, a 52-tone resource unit, and a 106-tone resource unit.

The non-contiguous channel allocation information may be indicated via acombination of a bandwidth field of the HE-SIG-A and a resource unitallocation field of the HE-SIG-B.

The bandwidth field may indicate total bandwidth information throughwhich the packet is transmitted and channel information to be puncturedwithin the total bandwidth, and the resource unit allocation field mayindicate additional puncturing information within the total bandwidth.

When the bandwidth field indicates puncturing of one of two 20 MHzchannels in a secondary 40 MHz channel in a total bandwidth of 80 MHz,the resource unit allocation field may indicate which 20 MHz channel inthe secondary 40 MHz channel is punctured.

When the bandwidth field indicates puncturing of a secondary 20 MHzchannel in a total bandwidth of 160 MHz or 80+80 MHz, the resource unitallocation field may indicate additional puncturing in a secondary 80MHz channel.

When the bandwidth field indicates puncturing of at least one of two 20MHz channels in a secondary 40 MHz channel in a total bandwidth of 160MHz or 80+80 MHz, the resource unit allocation field may indicate which20 MHz channel in the secondary 40 MHz channel is punctured.

When the bandwidth field indicates puncturing of at least one of two 20MHz channels in a secondary 40 MHz channel in a total bandwidth of 160MHz or 80+80 MHz, the resource unit allocation field may indicateadditional puncturing in a secondary 80 MHz channel.

When the packet is transmitted in a total bandwidth of 80 MHz or more,the non-contiguous channel allocation information may further includeinformation of a field (C26 field) indicating whether a user isallocated to a center 26-tone resource unit of 80 MHz.

An HE-SIG-B field of the packet may consist of HE-SIG-B content channel1 and HE-SIG-B content channel 2 in units of 20 MHz, and the C26 fieldmay be carried in both the HE-SIG-B content channel 1 and the HE-SIG-Bcontent channel 2.

When the packet is transmitted in a total bandwidth of 80 MHz, both of aC26 field carried in the HE-SIG-B content channel 1 and a C26 fieldcarried in the HE-SIG-B content channel 2 may indicate whether a user isallocated to a center 26-tone resource unit in the total bandwidth of 80MHz.

When the C26 field indicates assignment of the center 26-tone resourceunit, the user field corresponding to the center 26-tone resource unitmay be carried in a user specific field of the HE-SIG-B content channel1.

When the packet is transmitted in a total bandwidth of 160 MHz or 80+80MHz, the total bandwidth may consist of a first 80 MHz bandwidth and asecond 80 MHz bandwidth, a first C26 field carried in the HE-SIG-Bcontent channel 1 may indicate whether a user is allocated to a firstcenter 26-tone resource unit in the first 80 MHz bandwidth, and a secondC26 field carried in the HE-SIG-B content channel 2 may indicate whethera user is allocated to a second center 26-tone resource unit in thesecond 80 MHz bandwidth.

When the first C26 field indicates assignment of the first center26-tone resource unit, a user field corresponding to the first center26-tone resource unit may be carried in a user specific field of theHE-SIG-B content channel 1, and when the second C26 field indicatesassignment of the second center 26-tone resource unit, a user fieldcorresponding to the second center 26-tone resource unit may be carriedin a user specific field of the HE-SIG-B content channel 2.

Advantageous Effects

According to the embodiment of the present invention, non-contiguouschannel allocation information can be efficiently signaled.

According to an embodiment of the present invention, it is possible toincrease the total resource utilization rate in the contention-basedchannel access system and improve the performance of the wireless LANsystem.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a wireless LAN system according to an embodiment ofthe present invention.

FIG. 2 illustrates a wireless LAN system according to another embodimentof the present invention.

FIG. 3 illustrates a configuration of a station according to anembodiment of the present invention.

FIG. 4 illustrates a configuration of an access point according to anembodiment of the present invention.

FIG. 5 schematically illustrates a process in which a STA and an AP seta link.

FIG. 6 illustrates a carrier sense multiple access (CSMA)/collisionavoidance (CA) method used in wireless LAN communication.

FIG. 7 illustrates a method for performing a distributed coordinationfunction (DCF) using a request to send (RTS) frame and a clear to send(CTS) frame.

FIGS. 8 and 9 illustrate multi-user transmission methods according to anembodiment of the present invention.

FIG. 10 illustrates an embodiment of a legacy PPDU format and anon-legacy PPDU format.

FIG. 11 illustrates various HE PPDU formats and an indication methodthereof according to an embodiment of the present invention.

FIG. 12 illustrates HE PPDU formats according to an additionalembodiment of the present invention.

FIG. 13 illustrates a power save operation scenario based on a PPDUformat according to an embodiment of the present invention.

FIG. 14 illustrates an embodiment of a configuration of an HE-SIG-Afield according to the HE PPDU format.

FIG. 15 illustrates a configuration of an HE-SIG-B field according to anembodiment of the present invention.

FIG. 16 illustrates an encoding structure and a transmission method ofthe HE-SIG-B according to an embodiment of the present invention.

FIG. 17 illustrates a subfield configuration of the HE-SIG-B when aSIG-B compression field indicates a compression mode of the HE-SIG-B.

FIGS. 18 to 20 illustrate channel extension methods according toembodiments of the present invention.

FIGS. 21 to 23 illustrate transmission sequences of a non-contiguousPPDU according to embodiments of the present invention.

FIG. 24 illustrates a method of setting a TXOP of an MU transmissionprocess as an additional embodiment of the present invention.

FIGS. 25 to 31 illustrate methods of signaling non-contiguous channelallocation information according to various embodiments of the presentinvention.

FIGS. 32 to 34 illustrate non-contiguous channel allocation methodsaccording to various embodiments of the present invention.

FIGS. 35 to 37 illustrate embodiments of a resource unit filteringaccording to additional embodiments of the present invention.

FIGS. 38 to 42 illustrate methods of signaling an HE MU PPDU accordingto additional embodiments of the present invention.

FIGS. 43 to 44 illustrate embodiments in which a transmission using anHE MU PPDU is performed between a single STA and an AP.

FIGS. 45 to 46 illustrate methods of a non-contiguous channel allocationand a signaling thereof according to additional embodiments of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Terms used in the specification adopt general terms which are currentlywidely used by considering functions in the present invention, but theterms may be changed depending on an intention of those skilled in theart, customs, and emergence of new technology. Further, in a specificcase, there is a term arbitrarily selected by an applicant and in thiscase, a meaning thereof will be described in a corresponding descriptionpart of the invention. Accordingly, it should be revealed that a termused in the specification should be analyzed based on not just a name ofthe term but a substantial meaning of the term and contents throughoutthe specification.

Throughout this specification and the claims that follow, when it isdescribed that an element is “coupled” to another element, the elementmay be “directly coupled” to the other element or “electrically coupled”to the other element through a third element. Further, unless explicitlydescribed to the contrary, the word “comprise” and variations such as“comprises” or “comprising”, will be understood to imply the inclusionof stated elements but not the exclusion of any other elements.Moreover, limitations such as “or more” or “or less” based on a specificthreshold may be appropriately substituted with “more than” or “lessthan”, respectively.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2015-0186871, 10-2016-0004471, 10-2016-0005835,10-2016-0026683, 10-2016-00300006, 10-2016-0059182, 10-2016-0062422 and10-2016-0083756 filed in the Korean Intellectual Property Office and theembodiments and mentioned items described in the respective application,which forms the basis of the priority, shall be included in the DetailedDescription of the present application.

FIG. 1 is a diagram illustrating a wireless LAN system according to anembodiment of the present invention. The wireless LAN system includesone or more basic service sets (BSS) and the BSS represents a set ofapparatuses which are successfully synchronized with each other tocommunicate with each other. In general, the BSS may be classified intoan infrastructure BSS and an independent BSS (IBSS) and FIG. 1illustrates the infrastructure BSS between them.

As illustrated in FIG. 1 , the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STA5, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a wireless medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a non-AP STA, or an AP, or to both terms. A station forwireless communication includes a processor and a communication unit andaccording to the embodiment, may further include a user interface unitand a display unit. The processor may generate a frame to be transmittedthrough a wireless network or process a frame received through thewireless network and besides, perform various processing for controllingthe station. In addition, the communication unit is functionallyconnected with the processor and transmits and receives frames throughthe wireless network for the station. According to the presentinvention, a terminal may be used as a term which includes userequipment (UE).

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense. In the present invention, an AP may also be referredto as a base wireless communication terminal. The base wirelesscommunication terminal may be used as a term which includes an AP, abase station, an eNB (i.e. eNodeB) and a transmission point (TP) in abroad sense. In addition, the base wireless communication terminal mayinclude various types of wireless communication terminals that allocatemedium resources and perform scheduling in communication with aplurality of wireless communication terminals.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless LAN systemaccording to another embodiment of the present invention. In theembodiment of FIG. 2 , duplicative description of parts, which are thesame as or correspond to the embodiment of FIG. 1 , will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STAT are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STAT may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention. As illustrated inFIG. 3 , the station 100 according to the embodiment of the presentinvention may include a processor 110, a communication unit 120, a userinterface unit 140, a display unit 150, and a memory 160.

First, the communication unit 120 transmits and receives a wirelesssignal such as a wireless LAN packet, or the like and may be embedded inthe station 100 or provided as an exterior. According to the embodiment,the communication unit 120 may include at least one communication moduleusing different frequency bands. For example, the communication unit 120may include communication modules having different frequency bands suchas 2.4 GHz, 5 GHz, and 60 GHz. According to an embodiment, the station100 may include a communication module using a frequency band of 6 GHzor more and a communication module using a frequency band of 6 GHz orless. The respective communication modules may perform wirelesscommunication with the AP or an external station according to a wirelessLAN standard of a frequency band supported by the correspondingcommunication module. The communication unit 120 may operate only onecommunication module at a time or simultaneously operate multiplecommunication modules together according to the performance andrequirements of the station 100. When the station 100 includes aplurality of communication modules, each communication module may beimplemented by independent elements or a plurality of modules may beintegrated into one chip. In an embodiment of the present invention, thecommunication unit 120 may represent a radio frequency (RF)communication module for processing an RF signal.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the communication unit120, and the like. That is, the processor 110 may be a modem or amodulator/demodulator for modulating and demodulating wireless signalstransmitted to and received from the communication unit 120. Theprocessor 110 controls various operations of wireless signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the communication unit 120 may be implemented whilebeing integrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention. As illustrated inFIG. 4 , the AP 200 according to the embodiment of the present inventionmay include a processor 210, a communication unit 220, and a memory 260.In FIG. 4 , among the components of the AP 200, duplicative descriptionof parts which are the same as or correspond to the components of thestation 100 of FIG. 2 will be omitted.

Referring to FIG. 4 , the AP 200 according to the present inventionincludes the communication unit 220 for operating the BSS in at leastone frequency band. As described in the embodiment of FIG. 3 , thecommunication unit 220 of the AP 200 may also include a plurality ofcommunication modules using different frequency bands. That is, the AP200 according to the embodiment of the present invention may include twoor more communication modules among different frequency bands, forexample, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200 mayinclude a communication module using a frequency band of 6 GHz or moreand a communication module using a frequency band of 6 GHz or less. Therespective communication modules may perform wireless communication withthe station according to a wireless LAN standard of a frequency bandsupported by the corresponding communication module. The communicationunit 220 may operate only one communication module at a time orsimultaneously operate multiple communication modules together accordingto the performance and requirements of the AP 200. In an embodiment ofthe present invention, the communication unit 220 may represent a radiofrequency (RF) communication module for processing an RF signal.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. According to an embodiment, the processor210 may be a modem or a modulator/demodulator for modulating anddemodulating wireless signals transmitted to and received from thecommunication unit 220. The processor 210 controls various operationssuch as wireless signal transmission/reception of the AP 200 accordingto the embodiment of the present invention. A detailed embodimentthereof will be described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5 , the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b). In this specification, an association basically means awireless association, but the present invention is not limited thereto,and the association may include both the wireless association and awired association in a broad sense.

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5 , the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

FIG. 6 is a diagram illustrating a carrier sense multiple access(CSMA)/collision avoidance (CA) method used in wireless LANcommunication.

A terminal that performs a wireless LAN communication checks whether achannel is busy by performing carrier sensing before transmitting data.When a wireless signal having a predetermined strength or more issensed, it is determined that the corresponding channel is busy and theterminal delays the access to the corresponding channel. Such a processis referred to as clear channel assessment (CCA) and a level to decidewhether the corresponding signal is sensed is referred to as a CCAthreshold. When a wireless signal having the CCA threshold or more,which is received by the terminal, indicates the corresponding terminalas a receiver, the terminal processes the received wireless signal.Meanwhile, when a wireless signal is not sensed in the correspondingchannel or a wireless signal having a strength smaller than the CCAthreshold is sensed, it is determined that the channel is idle.

When it is determined that the channel is idle, each terminal havingdata to be transmitted performs a backoff procedure after an inter framespace (IFS) time depending on a situation of each terminal, forinstance, an arbitration IFS (AIFS), a PCF IFS (PIFS), or the likeelapses. According to the embodiment, the AIFS may be used as acomponent which substitutes for the existing DCF IFS (DIFS). Eachterminal stands by while decreasing slot time(s) as long as a randomnumber determined by the corresponding terminal during an interval of anidle state of the channel and a terminal that completely exhausts theslot time(s) attempts to access the corresponding channel. As such, aninterval in which each terminal performs the backoff procedure isreferred to as a contention window interval.

When a specific terminal successfully accesses the channel, thecorresponding terminal may transmit data through the channel. However,when the terminal which attempts the access collides with anotherterminal, the terminals which collide with each other are assigned withnew random numbers, respectively to perform the backoff procedure again.According to an embodiment, a random number newly assigned to eachterminal may be decided within a range (2*CW) which is twice larger thana range (a contention window, CW) of a random number which thecorresponding terminal is previously assigned. Meanwhile, each terminalattempts the access by performing the backoff procedure again in a nextcontention window interval and in this case, each terminal performs thebackoff procedure from slot time(s) which remained in the previouscontention window interval. By such a method, the respective terminalsthat perform the wireless LAN communication may avoid a mutual collisionfor a specific channel.

FIG. 7 is a diagram illustrating a method for performing a distributedcoordination function using a request to send (RTS) frame and a clear tosend (CTS) frame.

The AP and STAs in the BSS contend in order to obtain an authority fortransmitting data. When data transmission at the previous step iscompleted, each terminal having data to be transmitted performs abackoff procedure while decreasing a backoff counter (alternatively, abackoff timer) of a random number assigned to each terminal after anAFIS time. A transmitting terminal in which the backoff counter expirestransmits the request to send (RTS) frame to notify that correspondingterminal has data to transmit. According to an exemplary embodiment ofFIG. 7 , STA1 which holds a lead in contention with minimum backoff maytransmit the RTS frame after the backoff counter expires. The RTS frameincludes information on a receiver address, a transmitter address, andduration. A receiving terminal (i.e., the AP in FIG. 7 ) that receivesthe RTS frame transmits the clear to send (CTS) frame after waiting fora short IFS (SIFS) time to notify that the data transmission isavailable to the transmitting terminal STA1. The CTS frame includes theinformation on a receiver address and duration. In this case, thereceiver address of the CTS frame may be set identically to atransmitter address of the RTS frame corresponding thereto, that is, anaddress of the transmitting terminal STA1.

The transmitting terminal STA1 that receives the CTS frame transmits thedata after a SIFS time. When the data transmission is completed, thereceiving terminal AP transmits an acknowledgment (ACK) frame after aSIFS time to notify that the data transmission is completed. When thetransmitting terminal receives the ACK frame within a predeterminedtime, the transmitting terminal regards that the data transmission issuccessful. However, when the transmitting terminal does not receive theACK frame within the predetermined time, the transmitting terminalregards that the data transmission is failed. Meanwhile, adjacentterminals that receive at least one of the RTS frame and the CTS framein the course of the transmission procedure set a network allocationvector (NAV) and do not perform data transmission until the set NAV isterminated. In this case, the NAV of each terminal may be set based on aduration field of the received RTS frame or CTS frame.

In the course of the aforementioned data transmission procedure, whenthe RTS frame or CTS frame of the terminals is not normally transferredto a target terminal (i.e., a terminal of the receiver address) due to asituation such as interference or a collision, a subsequent process issuspended. The transmitting terminal STA1 that transmitted the RTS frameregards that the data transmission is unavailable and participates in anext contention by being assigned with a new random number. In thiscase, the newly assigned random number may be determined within a range(2*CW) twice larger than a previous predetermined random number range (acontention window, CW).

FIGS. 8 and 9 illustrate multi-user transmission methods according to anembodiment of the present invention. When using orthogonal frequencydivision multiple access (OFDMA) or multi-input multi-output (MIMO), onewireless communication terminal can simultaneously transmit data to aplurality of wireless communication terminals. Further, one wirelesscommunication terminal can simultaneously receive data from a pluralityof wireless communication terminals. For example, a downlink multi-user(DL-MU) transmission in which an AP simultaneously transmits data to aplurality of STAs, and an uplink multi-user (UL-MU) transmission inwhich a plurality of STAs simultaneously transmit data to the AP may beperformed.

FIG. 8 illustrates a UL-MU transmission process according to anembodiment of the present invention. In order to perform the UL-MUtransmission, the channel to be used and the transmission start time ofeach STA that performs uplink transmission should be adjusted. In orderto efficiently schedule the UL-MU transmission, state information ofeach STA needs to be transmitted to the AP. According to an embodimentof the present invention, information for scheduling of a UL-MUtransmission may be indicated through a predetermined field of apreamble of a packet and/or a predetermined field of a MAC header. Forexample, a STA may indicate information for UL-MU transmissionscheduling through a predetermined field of a preamble or a MAC headerof an uplink transmission packet, and may transmit the information to anAP. In this case, the information for UL-MU transmission schedulingincludes at least one of buffer status information of each STA, andchannel state information measured by each STA. The buffer statusinformation of the STA may indicate at least one of whether the STA hasuplink data to be transmitted, the access category (AC) of the uplinkdata and the size (or the transmission time) of the uplink data.

According to an embodiment of the present invention, the UL-MUtransmission process may be managed by the AP. The UL-MU transmissionmay be performed in response to a trigger frame transmitted by the AP.The STAs simultaneously transmit uplink data a predetermined IFS (e.g.,SIFS) time after receiving the trigger frame. The trigger frame solicitsUL-MU transmission of STAs and may inform channel (or subchannel)information allocated to the uplink STAs. Upon receiving the triggerframe from the AP, a plurality of STAs transmit uplink data through eachallocated channel (or, subchannel) in response thereto. After the uplinkdata transmission is completed, the AP transmits an ACK to the STAs thathave successfully transmitted the uplink data. In this case, the AP maytransmit a predetermined multi-STA block ACK (M-BA) as an ACK for aplurality of STAs.

In the non-legacy wireless LAN system, subcarriers of a specific number,for example, 26, 52, or 106 tones may be used as a resource unit (RU)for a subchannel-based access in a channel of 20 MHz band. Accordingly,the trigger frame may indicate identification information of each STAparticipating in the UL-MU transmission and information of the allocatedresource unit. The identification information of the STA includes atleast one of an association ID (AID), a partial AID, and a MAC addressof the STA. Further, the information of the resource unit includes thesize and placement information of the resource unit.

On the other hand, in the non-legacy wireless LAN system, a UL-MUtransmission may be performed based on a contention of a plurality ofSTAs for a specific resource unit. For example, if an AID field valuefor a specific resource unit is set to a specific value (e.g., 0) thatis not assigned to STAs, a plurality of STAs may attempt random access(RA) for the corresponding resource unit.

FIG. 9 illustrates a DL-MU transmission process according to anembodiment of the present invention. According to an embodiment of thepresent invention, RTS and/or CTS frames of a predetermined format maybe used for NAV setting in the DL-MU transmission process. First, the APtransmits a multi-user RTS (MU-RTS) frame for NAV setting in the DL-MUtransmission process. The duration field of the MU-RTS frame is set to atime until the end of the DL-MU transmission session. That is, theduration field of the MU-RTS frame is set based on a period until thedownlink data transmission of the AP and ACK frame transmissions of theSTAs are completed. The neighboring terminals of the AP set a NAV untilthe end of the DL-MU transmission session based on the duration field ofthe MU-RTS frame transmitted by the AP. According to an embodiment, theMU-RTS frame may be configured in the format of a trigger frame andrequests simultaneous CTS (sCTS) frame transmissions of the STAs.

STAs (e.g., STA1 and STA2) receiving the MU-RTS frame from the APtransmit the sCTS frame. The sCTS frames transmitted by a plurality ofSTAs have the same waveform. That is, the sCTS frame transmitted by theSTA1 on the first channel has the same waveform as the sCTS frametransmitted by the STA2 on the first channel According to an embodiment,the sCTS frame is transmitted on the channel indicated by the MU-RTSframe. The duration field of the sCTS frame is set to a time until theDL-MU transmission session is terminated based on the information of theduration field of the MU-RTS frame. That is, the duration field of thesCTS frame is set based on the period until the downlink datatransmission of the AP and the ACK frame transmissions of the STAs arecompleted. In FIG. 9 , neighboring terminals of STA1 and STA2 set a NAVuntil the end of the DL-MU transmission session based on the durationfield of the sCTS frame.

According to an embodiment of the present invention, the MU-RTS frameand the sCTS frame may be transmitted on a 20 MHz channel basis.Accordingly, the neighboring terminals including legacy terminals canset the NAV by receiving the MU-RTS frame and/or the sCTS frame. Whenthe transmission of the MU-RTS frame and the sCTS frame is completed,the AP performs a downlink transmission. FIG. 9 illustrates anembodiment in which the AP transmits DL-MU data to STA1 and STA2,respectively. The STAs receive the downlink data transmitted by the APand transmit an uplink ACK in response thereto.

FIG. 10 illustrates an embodiment of a legacy PLCP Protocol Data Unit(PPDU) format and a non-legacy PPDU format. More specifically, FIG.10(a) illustrates an embodiment of a legacy PPDU format based on802.11a/g, and FIG. 10(b) illustrates an embodiment of a non-legacy PPDUbased on 802.11ax. In addition, FIG. 10(c) illustrates the detailedfield configuration of L-SIG and RL-SIG commonly used in the PPDUformats.

Referring to FIG. 10(a), the preamble of the legacy PPDU includes alegacy short training field (L-STF), a legacy long training field(L-LTF), and a legacy signal field (L-SIG). In an embodiment of thepresent invention, the L-STF, L-LTF and L-SIG may be referred to as alegacy preamble. Referring to FIG. 10(b), the preamble of the HE PPDUincludes a repeated legacy short training field (RL-SIG), a highefficiency signal A field (HE-SIG-A), a high efficiency signal B field,a high efficiency short training field (HE-STF), and a high efficiencylong training field (HE-LTF) in addition to the legacy preamble. In anembodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B,HE-STF and HE-LTF may be referred to as a non-legacy preamble. Thedetailed configuration of the non-legacy preamble may be modifiedaccording to the HE PPDU format. For example, HE-SIG-B may only be usedin some formats among the HE PPDU formats.

A 64 FFT OFDM is applied to the L-SIG included in the preamble of thePPDU and the L-SIG consists of 64 subcarriers in total. Among these, 48subcarriers excluding guard subcarriers, a DC subcarrier and pilotsubcarriers are used for data transmission of the L-SIG. If a modulationand coding scheme (MCS) of BPSK, Rate=1/2 is applied, the L-SIG mayinclude information of a total of 24 bits. FIG. 10(c) illustrates aconfiguration of 24-bit information of the L-SIG.

Referring to FIG. 10(c), the L-SIG includes an L_RATE field and anL_LENGTH field. The L_RATE field consists of 4 bits and represents theMCS used for data transmission. More specifically, the L_RATE fieldrepresents one of the transmission rates of 6/9/12/18/24/24/36/48/54Mbps by combining the modulation scheme such as BPSK/QPSK/16-QAM/64-QAMwith the code rate such as 1/2, 2/3, 3/4. When combining the informationof the L_RATE field and the L_LENGTH field, the total length of thecorresponding PPDU can be represented. The non-legacy PPDU sets theL_RATE field to a 6 Mbps which is the minimum rate.

The L_LENGTH field consists of 12 bits, and may represent the length ofthe corresponding PPDU by a combination with the L_RATE field. In thiscase, the legacy terminal and the non-legacy terminal may interpret theL_LENGTH field in different ways.

First, a method of interpreting the length of a PPDU using a L_LENGTHfield by a legacy terminal or a non-legacy terminal is as follows. Whenthe L_RATE field is set to 6 Mbps, 3 bytes (i.e., 24 bits) can betransmitted for 4 us, which is one symbol duration of 64 FFT. Therefore,by adding 3 bytes corresponding to the SVC field and the Tail field tothe value of the L_LENGTH field and dividing it by 3 bytes, which is thetransmission amount of one symbol, the number of symbols after the L-SIGis obtained on the 64FFT basis. The length of the corresponding PPDU,that is, the reception time (i.e., RXTIME) is obtained by multiplyingthe obtained number of symbols by 4 us, which is one symbol duration,and then adding a 20 us which is for transmitting L-STF, L-LTF andL-SIG. This can be expressed by the following Equation 1.

$\begin{matrix}{{{RXTIME}({us})} = {{\left( \left\lceil \frac{{L{\_ LENGTH}} + 3}{3} \right\rceil \right) \times 4} + 20}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

In this case, ┌x┐ denotes the smallest natural number greater than orequal to x. Since the maximum value of the L_LENGTH field is 4095, thelength of the PPDU can be set up to 5.464 ms. The non-legacy terminaltransmitting the PPDU should set the L_LENGTH field as shown in Equation2 below.

$\begin{matrix}{{L{\_ LENGTH}({byte})} = {{\left( \left\lceil \frac{{TXTIME} - 20}{4} \right\rceil \right) \times 3} - 3}} & \left\lbrack {{Equation}2} \right\rbrack\end{matrix}$

Herein, TXTIME is the total transmission time constituting thecorresponding PPDU, and is expressed by Equation 3 below. In this case,TX represents the transmission time of X.

$\begin{matrix}{{{TXTIME}({us})} = {T_{L - {STF}} + T_{L - {LTF}} + T_{L - {SIG}} + T_{{RL} - {SIG}} + T_{{HE} - {SIG} - A} + \left( T_{{HE} - {SIG} - B} \right) + T_{{HE} - {STF}} + {N_{{HE} - {LTF}} \cdot T_{{HE} - {LTF}}} + T_{Data}}} & \left\lbrack {{Equation}3} \right\rbrack\end{matrix}$

With reference to the above equations, the length of the PPDU iscalculated based on the round-up value of L_LENGTH/3. Therefore, for anyvalue of k, three different values of L_LENGTH={3k+1, 3k+2, 3(k+1)}indicate the same PPDU length. According to an embodiment of the presentinvention, the non-legacy terminal may perform additional signalingusing three different L_LENGTH values indicating the same PPDU lengthinformation. More specifically, values corresponding to 3k+1 and 3k+2among the three different L_LENGTH values may be used to indicate the HEPPDU format.

FIG. 11 illustrates various HE PPDU formats and an indication methodthereof according to an embodiment of the present invention. Accordingto an embodiment of the present invention, the HE PPDU format may beindicated based on the L_LENGTH field and HE-SIG-A of the correspondingPPDU. More specifically, the HE PPDU format is indicated based on atleast one of the value of the L_LENGTH field and the modulation schemeapplied to the HE-SIG-A symbol.

First, referring to FIG. 11(a), when the value of the L_LENGTH field is3k+1 (i.e., when mod 3=1), the corresponding PPDU is an HE SU PPDU or anHE Trigger-based PPDU. The HE SU PPDU is a PPDU used for a single-usertransmission between an AP and a single STA. Furthermore, the HETrigger-based PPDU is an uplink PPDU used for a transmission that is aresponse to a trigger frame. HE SU PPDU and HE Trigger-based PPDU havethe same preamble format. In the cases of the HE SU PPDU and the HETrigger-based PPDU, two symbols of HE-SIG-A are modulated with BPSK andBPSK, respectively.

According to a further embodiment of the present invention illustratedin FIG. 11(b), when the value of the L_LENGTH field is 3k+1 and the twosymbols of HE-SIG-A are modulated with BPSK and QBPSK, respectively, thecorresponding PPDU is an extended PPDU. The extended PPDU is used as anew PPDU format other than the PPDU formats supported by 802.11ax.

Next, when the value of the L_LENGTH field is 3k+2 (i.e., when mod 3=2),the corresponding PPDU is an HE MU PPDU or an HE Extended Range (ER) SUPPDU. The HE MU PPDU is a PPDU used for a transmission to one or moreterminals. The HE MU PPDU format is illustrate in FIG. 11(c) andadditionally includes HE-SIG-B in the non-legacy preamble. In the caseof the HE MU PPDU, the two symbols of HE-SIG-A are modulated with BPSKand BPSK, respectively. On the other hand, HE ER SU PPDU is used for asingle-user transmission with a terminal in an extended range. The HE ERSU PPDU format is illustrated in FIG. 11(d), where HE-SIG-A of thenon-legacy preamble is repeated on the time axis. In the case of the HEER SU PPDU, the first two symbols of HE-SIG-A are modulated with BPSKand QBPSK, respectively. Thus, the non-legacy terminal can signal thePPDU format through the modulation scheme used for the two symbols ofHE-SIG-A in addition to the value of the L_LENGTH field.

The HE MU PPDU illustrated in FIG. 11(c) may be used by an AP to performa downlink transmission to a plurality of STAs. In this case, the HE MUPPDU may include scheduling information for a plurality of STAs tosimultaneously receive the corresponding PPDU. In addition, the HE MUPPDU may be used by a single STA to perform an uplink transmission tothe AP. In this case, the HE MU PPDU may transmit AID information of thereceiver and/or the transmitter of the corresponding PPDU through a userspecific field of the HE-SIG-B. Therefore, terminals receiving the HE MUPPDU may perform a spatial reuse operation based on the AID informationobtained from the preamble of the corresponding PPDU. In addition, datatransmission through some narrowband may be performed using the HE MUPPDU. Here, the narrowband may be a frequency band of less than 20 MHz.According to an embodiment, the HE MU PPDU may indicate allocationinformation of resource unit(s) to be used for a narrowband transmissionthrough the HE-SIG-B.

More specifically, the resource unit allocation (RA) field of HE-SIG-Bcontains information on the resource unit partition type in a specificbandwidth (e.g., 20 MHz) of the frequency domain. Further, informationof a STA assigned to each partitioned resource unit may be transmittedthrough the user specific field of the HE-SIG-B. The user specific fieldincludes one or more user fields corresponding to each partitionedresource unit.

When a narrowband transmission using a part of the partitioned resourceunits is performed, the resource unit used for the transmission may beindicated through the user specific field of the HE-SIG-B. According toan embodiment, an AID of a receiver or a transmitter may be contained ina user field corresponding to resource unit(s) on which datatransmission is performed among a plurality of partitioned resourceunits. In addition, a predetermined Null STA ID may be contained in userfield(s) corresponding to the remaining resource unit(s) in which datatransmission is not performed. According to another embodiment of thepresent invention, the narrowband transmission may be signaled through afirst user field corresponding to a resource unit in which datatransmission is not performed and a second user field corresponding to aresource unit in which data transmission is performed. Morespecifically, a predetermined null STA ID may be contained in the firstuser field, and the placement information of the resource unit(s) onwhich data transmission is performed may be indicated through theremaining subfields of the corresponding user field. Next, the AID ofthe receiver or transmitter may be contained in the second user field.Thus, the terminal may signal the narrowband transmission through thelocation information contained in the first user field and the AIDinformation contained in the second user field. In this case, since userfields less than the number of partitioned resource units are used, thesignaling overhead can be reduced.

FIG. 12 illustrates HE PPDU formats according to an additionalembodiment of the present invention. In each embodiment of FIG. 12 , itis illustrated that, in the HE PPDU, the L_LENGTH field has a value of3k+1 (i.e., mod 3=1) and the two symbols of HE-SIG-A are modulated withBPSK and QBPSK, respectively, but the present invention is not limitedthereto. That is, in each embodiment of the HE PPDU, the L_LENGTH fieldmay have a value of 3k+2 (i.e., mod 3=2) or the two symbols of HE-SIG-Amay be modulated with BPSK and BPSK, respectively,

First, FIG. 12(a) illustrates an HE ER PPDU format according to anembodiment of the present invention. In the corresponding PPDU format,HE-SIG-A and HE-SIG-B are repeated in the time domain. In this case, itis possible to obtain a reception gain of 3 dB or more due to repetitivetransmission of HE-SIG-A and HE-SIG-B in the time domain, therebyenabling signal reception at a long distance. Since the PPDU formataccording to the embodiment of FIG. 12(a) can additionally signalHE-SIG-B, it can be used for a downlink extended range (ER) multi-usertransmission. In addition, the corresponding PPDU format may be used fornarrowband transmission of data in uplink/downlink ER single-usertransmissions. More specifically, the PPDU format may signal, viaHE-SIG-B, a transmission which uses a part of the resource units of thedata area transmitted on the basis of 256 FFT/20 MHz. Therefore,transmission using only 26-tone RU, 52-tone RU, or 106-tone RU which isless than 20 MHz band can be performed even in an uplink/downlinksingle-user transmission situation. Through such narrowbandtransmission, the terminal can perform transmission by concentrating theentire allowable transmission power in the ISM band on a narrow RU. Thatis, in addition to the extension of the transmission distance due to therepetitive transmission of the HE-SIG-A/B in the 64 FFT/20 MHz domain,the transmission distance can be extended even in the data transmissionin the following 256 FFT/20 MHz domain. In addition, the correspondingPPDU format may also be used for narrowband transmission of data in adownlink multi-user transmission. For example, as shown in FIG. 12(a),the AP may indicate partition information of the 20 MHz band viaHE-SIG-B of the PPDU, and use some resource units including at least twoof the partitioned resource units for the narrowband transmission. Inthis case, the transmission distance can be increased by concentratingthe entire allowable transmission power in the ISM band to some resourceunits and transmitting it.

Next, FIG. 12(b) illustrates an HE ER PPDU format according to anotherembodiment of the present invention. In the corresponding PPDU format,HE-SIG-A is repeated in the time domain, and HE-SIG-B is not transmittedin order to reduce the preamble overhead. In this case, it is possibleto obtain a reception gain of 3 dB or more due to repetitivetransmission of HE-SIG-A in the time domain, thereby enabling signalreception at a long distance. According to an embodiment, thedistinction between the PPDU format according to FIG. 12(a) and the PPDUformat according to FIG. 12(b) may be indicated through a predeterminedfield of the HE-SIG-A. The PPDU format according to the embodiment ofFIG. 12(b) may be used for narrowband transmission of data inuplink/downlink ER single-user transmission. In this case, thecorresponding PPDU format may indicate a transmission using a specificresource unit of a data area transmitted on the basis of 256 FFT/20 MHzwithout signaling via HE-SIG-B. For example, transmission only usingsome predetermined resource units within the 20 MHz bandwidth may beindicated via a specific field (e.g., Bandwidth field) of the HE-SIG-A.In this case, the some predetermined resource units may be at least oneof 26-tone RU, 52-tone RU, and 106-tone RU in a specific placement. Apredetermined field of the HE-SIG-A in the HE ER PPDU may indicatewhether transmission using some predetermined resource units isperformed or transmission using a 20 MHz full band (i.e., 242-tone RU)is performed. As described above, according to the embodiment of FIG.12(b), the predetermined narrowband transmission may be indicated bysimple signaling of the HE-SIG-A without using the HE-SIG-B in the HE ERPPDU.

Next, FIG. 12(c) illustrates an HE ER PPDU format according to yetanother embodiment of the present invention. In the corresponding PPDUformat, HE-SIG-A is repeated in the time domain, and HE-SIG-B is nottransmitted in order to reduce the preamble overhead. Instead, HE-SIG-Ctransmitted in the 256 FFT/20 MHz domain may additionally be used. Inthis case, it is possible to obtain a reception gain of 3 dB or more dueto repetitive transmission of HE-SIG-A in the time domain, therebyenabling signal reception at a long distance. The corresponding PPDUformat may indicate a transmission using a specific resource unit of adata area transmitted on the basis of 256 FFT/20 MHz without signalingvia HE-SIG-B. The specific embodiments thereof are as described in theembodiment of FIG. 12(b). The HE-SIG-C may transmit information for aterminal to decode data transmitted through the corresponding resourceunit, for example, MCS, whether a transmit beamforming (TxBF) isapplied, binary convolutional code (BCC)/low density parity check (LDPC)coding indicator, and the like.

Finally, FIG. 12(d) illustrates an HE PPDU format according to stillanother embodiment of the present invention. In the corresponding PPDUformat, HE-SIG-A is not repeated in the time domain, and HE-SIG-B is nottransmitted. Instead, a HE-SIG-C transmitted in the 256 FFT/20 MHzdomain may additionally be used. The PPDU according to the embodiment ofFIG. 12(d) may be used to allow the neighboring STAs of the AP to set aNAV using the transmission opportunity (TXOP) duration informationincluded in the HE-SIG-A. The corresponding PPDU format may indicate atransmission using a specific resource unit of a data area transmittedon the basis of 256 FFT/20 MHz without signaling via HE-SIG-B. Thespecific embodiments thereof are as described in the embodiment of FIG.12(b). The HE-SIG-C may transmit information for a terminal to decodedata transmitted through the corresponding resource unit as describedabove.

FIG. 13 illustrates a power save operation scenario based on a PPDUformat according to an embodiment of the present invention. In a BSSoperated by a non-legacy AP, a STA (i.e., ER STA) that supports anextended range (ER) mode and a STA (i.e., a non-ER STA) that does notsupport the ER mode may be mixed. In the embodiment of FIG. 13 , STA “A”represents a non-ER STA, and STA “B” represents an ER STA.

According to the embodiment of the present invention, when the non-ERSTA receives an ER PPDU of the same BSS (i.e., intra-BSS), it can enterthe power save mode. In the embodiment of FIG. 13 , the AP exchanges anER SU PPDU with the STA “B”, and the STA “A” receiving the correspondingPPDU enters the power save mode for the length of the received PPDU. TheSTA negotiates whether or not to support the ER mode when performing anassociation with the AP. Therefore, when the non-ER STA receives the ERPPDU of the same BSS, it can enter the power save mode withoutadditional processing because it is obvious that the corresponding PPDUis not a PPDU transmitted to itself.

FIG. 14 illustrates an embodiment of a configuration of an HE-SIG-Afield according to the HE PPDU format. HE-SIG-A consists of two symbolsof 64 FFT, and indicates common information for reception of the HEPPDU. The first symbol of the HE-SIG-A is modulated with BPSK, and thesecond symbol of the HE-SIG-A is modulated with BPSK or QBPSK. In the HEER SU PPDU, two symbols of the HE-SIG-A may be repeatedly transmitted.That is, the HE-SIG-A of the HE ER SU PPDU consists of four symbols, thefirst symbol and the second symbol of which have the same data bit, andthe third symbol and the fourth symbol of which have the same data bit.

First, FIG. 14(a) illustrates a subfield configuration of the HE-SIG-Afield of the HE SU PPDU. According to an embodiment, the HE-SIG-A fieldof the HE ER SU PPDU may be configured similarly. The function of eachfield included in HE-SIG-A will be described as follows.

The UL/DL field indicates a transmission direction of the correspondingPPDU. That is, the corresponding field indicates whether thecorresponding PPDU is transmitted with uplink or is transmitted withdownlink. The format field is used to differentiate an HE SU PPDU froman HE Trigger-based PPDU. The BSS color field consists of 6 bits andindicates an identifier of the BSS corresponding to a terminal thattransmitted the corresponding PPDU. The spatial reuse field carriesinformation such as signal to interference plus noise ratio (SINR),transmission power, etc., which can be referred to by terminals toperform spatial reuse transmission during the transmission of thecorresponding PPDU.

The TXOP duration field indicates duration information for TXOPprotection and NAV setting. The corresponding field sets the duration ofthe TXOP interval in which consecutive transmission is to be performedafter the corresponding PPDU, so that the neighboring terminals set aNAV for the corresponding duration. The bandwidth field indicates thetotal bandwidth in which the corresponding PPDU is transmitted.According to an embodiment, the bandwidth field may consist of 2 bitsand indicate one of 20 MHz, 40 MHz, 80 MH and 160 MHz (including 80+80MHz). The MCS field indicates an MCS value applied to the data field ofthe corresponding PPDU. The CP+LTF size field indicates the duration ofthe cyclic prefix (CP) or guard interval (GI) and the size of theHE-LTF. More specifically, the corresponding field indicates thecombination of the HE-LTF size used among 1×, 2×, and 4×HE-LTF, and theCP (or GI) value used in the data field among 0.8 us, 1.6 us, and 3.2us.

The coding field may indicate which coding scheme is used between binaryconvolutional code (BCC) and low density parity check (LDPC). Inaddition, the corresponding field may indicate whether an extra OFDMsymbol for LDPC is present. The number of space time streams (NSTS)field indicates the number of space-time streams used for MIMOtransmission. The space time block coding (STBC) field indicates whetherspace-time block coding is used. The transmit beamforming (TxBF) fieldindicates whether beamforming is applied to the transmission of thecorresponding PPDU. The dual carrier modulation (DCM) field indicateswhether dual carrier modulation is applied to the data field. The dualcarrier modulation transmits the same information through twosubcarriers in order to cope with narrowband interference. The packetextension field indicates which level of packet extension is applied tothe PPDU. The beam change field indicates whether the part before theHE-STF of the corresponding PPDU is mapped spatially different from theHE-LTF. The CRC field and the tail field are used to determine theauthenticity of the HE-SIG-A field information and to initialize the BCCdecoder, respectively.

Next, FIG. 14(b) illustrates a subfield configuration of the HE-SIG-Afield of the HE MU PPDU. Among the subfields shown in FIG. 14(b), thesame subfields as those shown in FIG. 14(a) will not be described.

The UL/DL field indicates the transmission direction of thecorresponding PPDU. That is, the corresponding field indicates whetherthe corresponding PPDU is transmitted with uplink or is transmitted withdownlink. The bandwidth field of the HE MU PPDU may indicate extrabandwidths in addition to the bandwidths of the HE SU PPDU. That is, thebandwidth field of the HE MU PPDU consists of 3 bits and indicates oneof 20 MHz, 40 MHz, 80 MHz, 160 MHz (including 80+80 MHz), andpredetermined non-contiguous bands. The specific embodiments of thepredetermined non-contiguous bands will be described later.

The SIG-B MCS field indicates the MCS applied to the HE-SIG-B field.Depending on the amount of information that requires signaling, variableMCS between MSC0 and MSC5 can be applied to the HE-SIG-B. The CP+LTFsize field indicates the duration of the CP or GI and the size of theHE-LTF. The corresponding field indicates the combination of the HE-LTFsize used among 2× and 4×HE-LTF, and the CP (or GI) value used in thedata field among 0.8 us, 1.6 us, and 3.2 us.

The SIG-B compression field indicates whether to use a compression modeof the HE-SIG-B field. When the HE MU PPDU is transmitted using anMU-MIMO in the full bandwidth, the resource unit allocation informationfor each 20 MHz band becomes unnecessary. Therefore, in the fullbandwidth MU-MIMO transmission, the SIG-B compression field indicatesthe compression mode of the HE-SIG-B field. In this case, the commonblock field containing the resource unit allocation field is not presentin the HE-SIG-B field. The SIG-B DCM field indicates whether theHE-SIG-B field is modulated with the DCM for reliable transmission ofthe HE-SIG-B field. The number of HE-SIG-B symbols field indicatesinformation on the number of OFDM symbols in the HE-SIG-B field.

On the other hand, when the HE MU PPDU is transmitted in a band of 40MHz or more as described later, the HE-SIG-B may consist of two kinds ofcontent channels in units of 20 MHz. The content channels are referredto as HE-SIG-B content channel 1 and HE-SIG-B content channel 2,respectively. According to an embodiment of the present invention, thenumber of HE-SIG-B symbols in each channel can be kept similar bydifferentiating MCSs applied to the HE-SIG-B content channel 1 and theHE-SIG-B content channel 2, respectively. The HE-SIG-A field of the HEMU PPDU may include a SIG-B dual MCS field. In this case, it isindicated through the corresponding field whether the MCSs applied tothe HE-SIG-B content channel 1 and the HE-SIG-B content channel 2 aredifferent with each other.

According to the embodiment of the present invention, when the SIG-Bcompression field indicates the compression mode of the HE-SIG-B field(i.e., when the full bandwidth MU-MIMO transmission is indicated), aspecific field of the HE-SIG-A may indicate information on the number ofMU-MIMO users. For example, when the full bandwidth MU-MIMO transmissionis performed, the HE-SIG-B content channel 1 and the HE-SIG-B contentchannel 2 do not need to distribute the amount of information throughdifferent MCSs. Therefore, when the SIG-B compression field indicatesthe compression mode of the HE-SIG-B field, the SIG-B dual MCS field ofthe HE-SIG-A may indicate information on the number of MU-MIMO users.Likewise, when the full bandwidth MU-MIMO transmission is performed,information on the number of symbols in each HE-SIG-B content channelneed not be delivered separately. Therefore, when the SIG-B compressionfield indicates the compression mode of the HE-SIG-B field, the numberof HE-SIG-B symbols field in the HE-SIG-A may indicate the informationon the number of MU-MIMO users. As described above, in the compressionmode in which the resource unit allocation field of the HE-SIG-B isomitted, information on the number of MU-MIMO users may be indicatedthrough a specific subfield of the HE-SIG-A.

According to an embodiment of the present invention, the HE MU PPDU maybe used for the DL-MU transmission. However, in the following additionalsituations, the HE MU PPDU may be used for both the downlinktransmission and the uplink transmission.

According to an embodiment, an HE MU PPDU may be used for OFDMA basedtransmission in a downlink/uplink transmission between an AP and asingle STA. More specifically, transmission between an AP and a singleSTA may be performed using only some contiguous or non-contiguouschannels among the entire band. For example, when only a secondary 20MHz channel is busy as a result of the STA performing CCA to transmit an80 MHz PPDU to the AP, the STA may transmit the PPDU through the primary20 MHz channel and the secondary 40 MHz channel. In addition, anarrowband transmission using only some resource units within 20 MHz maybe performed between an AP and a single STA. In the case where thetransmission using the non-contiguous channel or the narrowbandtransmission is performed, the resource unit allocation informationshould be additionally transmitted via the HE-SIG-B field in thetransmitted PPDU. Therefore, the terminal may perform such transmissionsusing the HE MU PPDU. The specific embodiments of the transmission usingthe non-contiguous channel and the narrowband transmission will bedescribed later.

According to another embodiment, the HE MU PPDU may be used when atransmission of the HE-SIG-B field is required for the enhancement ofthe spatial reuse operation. Unlike the HE SU PPDU, the HE MU PPDU canindicate an AID of the recipient through the user field of the HE-SIG-B.However, according to an exemplary embodiment of the present invention,since it is obvious that the recipient of the corresponding PPDU is anAP when the HE MU PPDU is used for an uplink transmission, the userfield of the HE-SIG-B may indicate an AID of the transmitter. Theneighboring terminals that have received the HE MU PPDU may perform thespatial reuse operation.

For example, assume that there are arbitrary BSS1 and BSS2, and thatSTA1 of the BSS1 transmits an HE UL MU PPDU. A STA of the BSS2overhearing the PPDU may estimate the distance between it and an AP ofthe BSS1 which is the recipient of the PPDU, through a DL PPDU of the APof the BSS1 that has been previously received. Therefore, the STA of theBSS2 may perform the spatial reuse operation considering theinterference to the AP of the BSS1 which is the recipient. Also, when aDL PPDU transmitted by the AP of the BSS1 to the STA1 of the BSS1 isreceived, the STA of the BSS2 may perform the spatial reuse operationconsidering the interference to the STA1 of the BSS1 which is therecipient of the corresponding PPDU. In this case, the interference isconsidered based on the signal strength previously measured from an HEUL MU PPDU of the STA1. In the spatial reuse operation, the STA mayattempt to transmit if the received PPDU is a PPDU of other BSS (OBSS)and the interference to the recipient of the corresponding PPDU is belowa predetermined level.

Next, FIG. 14(c) illustrates a subfield configuration of the HE-SIG-Afield of the HE trigger-based PPDU. Among the subfields shown in FIG.14(c), the same subfields as those shown in FIG. 14(a) or 14(b) will notbe described.

The format field is used to differentiate an HE SU PPDU from an HETrigger-based PPDU. Also, the HE Trigger-based PPDU includes theabove-described BSS color field and TXOP duration field. The spatialreuse field of the HE Trigger-based PPDU consists of 16 bits and carriesinformation for spatial reuse operation in units of 20 MHz or 40 MHzaccording to the total bandwidth. The bandwidth field consists of 2 bitsand may indicate one of 20 MHz, 40 MHz, 80 MHz and 160 MHz (including80+80 MHz).

FIG. 15 illustrates a configuration of an HE-SIG-B field according to anembodiment of the present invention. The HE-SIG-B field is present inthe HE MU PPDU and is transmitted in units of 20 MHz. In addition, theHE-SIG-B field indicates information necessary for receiving the HE MUPPDU. As illustrated in FIG. 15(a), the HE-SIG-B consists of a commonblock field and a user specific field.

FIG. 15(b) illustrates an embodiment of a subfield configuration of thecommon block field of the HE-SIG-B. First, the common block fieldincludes a resource unit allocation (RA) field. FIG. 15(c) illustratesan embodiment of the RA field.

Referring to FIG. 15(c), the RA field contains information on resourceunit allocation of a specific bandwidth (e.g., 20 MHz) in the frequencydomain. More specifically, the RA field consists in units of 8 bits, andindexes the size of the resource units constituting the specificbandwidth and their placement in the frequency domain. Further, the RAfield may indicate the number of users in each resource unit. When thetotal bandwidth through which the PPDU is transmitted is greater than apredetermined bandwidth (e.g., 40 MHz), the RA field may be set to amultiple of 8 bits to carry information in units of the specificbandwidth.

Each partitioned resource unit is generally assigned to one user.However, resource units of a certain bandwidth (e.g., 106-tones) or morecan be assigned to a plurality of users using MU-MIMO. In this case, theRA field may indicate the number of users in the corresponding resourceunit. In addition, the RA field may indicate, through a predeterminedindex, a specific resource unit in which a user specific field is nottransmitted, i.e., a specific resource unit (i.e., an empty RU) that isnot assigned to the user. According to an embodiment, the specificresource unit includes a resource unit (RU) having a bandwidth of amultiple of 20 MHz channels, i.e., 242-tone RU, 484-tone RU, 996-toneRU, and the like. In an empty RU indicated by the index value, datatransmission is not performed. In this manner, the terminal may signalnon-contiguous channel allocation information in units of 20 MHz througha predetermined index of the RA field of the HE-SIG-B.

According to an embodiment of the present invention, when a PPDU istransmitted through a total bandwidth of 80 MHz or more, the commonblock field further includes a field (hereinafter, referred to as C26field) indicating whether a user is allocated to a center 26-tone RU of80 MHz. The C26 field may consist of a 1-bit indicator before or afterthe RA field in the common block field.

On the other hand, the user specific field consists of a plurality ofuser fields, and carries information for a designated STA to eachallocated resource unit. The total number of user fields to be includedin the user specific field may be determined based on the RA field andthe C26 field. A plurality of user fields are transmitted in units of auser block field. The user block field is made up of an aggregation oftwo user fields, a CRC field and a tail field. Depending on the totalnumber of user fields, the last user block field may contain informationfor one or two STAs. For example, if a total of three users (i.e., STA1,STA2, and STA3) are designated, information for STA1 and STA2 may becoded and transmitted along with the CRC/tail field in the first userblock field, and information for STA3 may be coded and transmitted alongwith the CRC/tail field in the last user block field.

FIGS. 15(d)-1 and 15(d)-2 illustrate embodiments of the subfieldconfiguration of the user field of the HE-SIG-B, respectively. FIG.15(d)-1 illustrates a user field for an OFDMA transmission, and FIG.15(d)-2 illustrates a user field for a MU-MIMO transmission. Each userfield indicates a receiver AID of the corresponding resource unit.Exceptionally, when the HE MU PPDU is used for an uplink transmission,the user field may indicate a transmitter AID. When one user isallocated to one resource unit (i.e., non-MU-MIMO allocation), the userfield includes a number of spatial streams (NSTS) field, a TxBF field,an MCS field, a DCM field and a coding field as illustrated in FIG.15(d)-1. On the other hand, when a plurality of users are allocated toone resource unit (i.e., MU-MIMO allocation), the user field includes aspatial configuration field (SCF), an MCS field, a DCM field, and acoding field as illustrated in FIG. 15(d)-2. Each STA that receives aPPDU through an MU-MIMO allocation should identify the location andnumber of spatial streams for it in the corresponding resource unit. Tothis end, the user field for the MU-MIMO transmission includes a spatialconfiguration field (SCF).

FIG. 15(e) illustrates an embodiment of the SCF of the HE-SIG-B. The SCFindicates the number of spatial streams for each STA and the totalnumber of spatial streams in the MU-MIMO allocation. Each STA identifiesthe OFDMA and/or MIMO allocation of the corresponding PPDU through theRA field and identifies whether the STA receives data through theMU-MIMO allocation according to the order indicated in the user specificfield. When the STA receives data through the non-MU-MIMO allocation,the user field is interpreted according to the format of FIG. 15(d)-1.However, when the STA receives data through the MU-MIMO allocation, theuser field is interpreted according to the format of FIG. 15(d)-2. Onthe other hand, when the SIG-B compression field indicates the fullbandwidth MU-MIMO, the RA field is not present in the HE-SIG-B. In thiscase, since all the STAs signaled in the user specific field receivedata through the MU-MIMO allocation, the STAs interpret the user fieldaccording to the format of FIG. 15(d)-2.

FIG. 16 illustrates an encoding structure and a transmission method ofthe HE-SIG-B according to an embodiment of the present invention. FIG.16(a) illustrates the encoding structure of the HE-SIG-B, and FIG. 16(b)illustrates the transmission method of the HE-SIG-B in a bandwidth of 40MHz or more.

Referring to FIG. 16(a), the HE-SIG-B consists of a common block fieldand a user specific field. The detailed configuration of the commonblock field and the user specific field is as described in theembodiment of FIG. 15 . Each user field of the user specific field isarranged in order of allocated users in the resource unit arrangementindicated by the RA field of the common block field.

The user specific field consists of a plurality of user fields, and aplurality of user fields are transmitted in units of a user block field.As described above, the user block field is made up of an aggregation oftwo user fields, a CRC field, and a tail field. If the total number ofuser fields is odd, the last user block field may contain one userfield. At the end of the HE-SIG-B, padding may be added along the OFDMsymbol boundary.

Referring to FIG. 16(b), HE-SIG-B is separately encoded on each 20 MHzband. In this case, the HE-SIG-B may consist of a maximum of twocontents in units of 20 MHz, that is, an HE-SIG-B content channel 1 andan HE-SIG-B content channel 2. In the embodiment of FIG. 16(b), each boxrepresents a 20 MHz band, and “1” and “2” in the boxes represent theHE-SIG-B content channel 1 and the HE-SIG-B content channel 2,respectively. Each HE-SIG-B content channel in the total band isarranged in order of the physical frequency band. That is, the HE-SIG-Bcontent channel 1 is transmitted in the lowest frequency band, and theHE-SIG-B content channel 2 is transmitted in the next higher frequencyband. Such a content channel configuration is then duplicated throughcontent duplication in the next higher frequency bands. For example, forthe first to fourth channels with an increasing order of the frequencyconstituting the entire 80 MHz band, the HE-SIG-B content channel 1 istransmitted on the first channel and the third channel, and the HE-SIG-Bcontent channel 2 is transmitted on the second channel and the fourthchannel. Likewise, for the first to eighth channels with an increasingorder of the frequency constituting the entire 160 MHz band, theHE-SIG-B content channel 1 is transmitted on the first channel, thethird channel, the fifth channel and the seventh channel, and theHE-SIG-B content channel 2 is transmitted on the second channel, thefourth channel, the sixth channel and the eighth channel. When theterminal can decode the HE-SIG-B content channel 1 through at least onechannel and decode the HE-SIG-B content channel 2 through the other atleast one channel, information on the MU PPDU configuration of the totalbandwidth can be obtained. On the other hand, when the total bandwidthis 20 MHz, only one SIG-B content channel is transmitted.

FIG. 17 illustrates a subfield configuration of the HE-SIG-B when aSIG-B compression field indicates a compression mode of the HE-SIG-B. Asdescribed above, when the SIG-B compression field indicates thecompression mode (i.e., the full bandwidth MU-MIMO), the RA field is notpresent in the HE-SIG-B. Therefore, when an MU-MIMO transmission isperformed through a bandwidth greater than 20 MHz, the number of usersto be allocated to the HE-SIG-B content channel 1 and the HE-SIG-Bcontent channel 2, respectively, should be separately determined.According to an embodiment of the present invention, when the MU-MIMOtransmission is performed through a bandwidth greater than 20 MHz, userfields may be split equitably between the two content channels for loadbalancing. That is, the number of user fields transmitted in each SIG-Bcontent channel is determined as a round up or down value of a half thetotal number of users. For example, when the total number of user fieldsis k, the first to the ceil(k/2)-th user fields may be transmittedthrough the HE-SIG-B content channel 1, and the ceil(k/2)-th to the k-thuser fields may be transmitted through the HE-SIG-B content channel 2.If k is an odd number, the number of user fields included in theHE-SIG-B content channel 1 may be one more than the number of userfields included in the HE-SIG-B content channel 2.

Hereinafter, channel extension methods according to embodiments of thepresent invention will be described with reference to FIGS. 18 to 20 .In the embodiments of FIGS. 18 to 20 , CH1 to CH4 refer to respective 20MHz channels through which an 80 MHz PPDU is transmitted. Also, CH1 toCH8 refer to respective 20 MHz channels through which a 160 MHz PPDU or80+80 MHz PPDU is transmitted. In this case, it is designated that CH3is a primary 20 MHz channel (hereinafter, referred to as P20 channel),CH4 is a secondary 20 MHz channel (hereinafter, referred to as S20channel), and CH1 and CH2 are a secondary 40 MHz secondary channel(hereinafter, referred to as S40 channel), respectively. In addition, itis designated that CH5 to CH8 are a secondary 80 MHz channel(hereinafter, referred to as S80 channel).

First, FIG. 18 illustrates a wideband access method according to anembodiment of the present invention. After the transmission of theprevious PPDU is completed, the terminal having data to be transmittedperforms a backoff procedure on the P20 channel. The backoff proceduremay be started when the P20 channel is idle for an AIFS time. Theterminal obtains a backoff counter within a range of a contention window(CW) for the backoff procedure. The terminal performs a CCA anddecreases the backoff counter by one when the channel is idle. If thechannel is busy, the terminal suspends the backoff procedure and resumesthe backoff procedure an AIFS time after when the channel is idle again.When the backoff counter expires through the backoff procedure, theterminal may transmit data. In this case, the terminal performs a CCAfor the secondary channels to transmit data for a PIFS time before thebackoff counter expires. In the embodiment of FIG. 18 , the terminalattempts to transmit an 80 MHz PPDU, and some secondary channels, thatis, the S20 channel is detected as busy in the CCA procedure.

When at least a part of the secondary channels on which the CCA isperformed are busy, the PPDU transmission bandwidth of the terminal isdetermined based on the wideband access method. First, FIG. 18(a)illustrates a wideband access method according to a dynamic bandwidthoperation. According to the dynamic bandwidth operation, since the S20channel is busy, the terminal transmits data using only a certainbandwidth, that is, P20 channel according to the conventional channelextension rule. Meanwhile, FIG. 18(b) illustrates a wideband accessmethod according to a static bandwidth operation. According to thestatic bandwidth operation, since some channels for transmission arebusy, the data transmission in the entire bandwidth is delayed. Theterminal performs the backoff procedure again using a new backoffcounter, and the terminal transmits data using the entire bandwidth whenall the channels for the transmission are idle in the CCA before thebackoff counter expires. As described above, in the wideband accessmethods according to the embodiment of FIG. 18 , the bandwidth of thetransmitted PPDU may be greatly reduced or the transmission of the PPDUmay be delayed depending on the state of some secondary channels.

FIG. 19 illustrates a wideband access method according to anotherembodiment of the present invention. FIGS. 19(a) to 19(e) illustratesituations in which a wideband PPDU is transmitted based on differentchannel extension techniques, respectively. In each embodiment of FIG.19 , a fixed channel extension method refers to a channel extensionmethod of predetermined unit(s) according to the conventional extensionrule in order of 20 MHz, 40 MHz, 80 MHz, and 160 MHz. In addition, aflexible channel extension method refers to a channel extension methodof a 20 MHz unit in order of 20 MHz, 40 MHz, 60 MHz, 80 MHz, 100 MHz,120 MHz, 140 MHz and 160 MHz. In addition, a contiguous channelextension method refers to a channel extension method in which a bandoccupied by a transmitted PPDU always consists of contiguous channels.Also, a non-contiguous channel extension method refers to a channelextension method in which a band occupied by a transmitted PPDU includesat least one non-contiguous channel. In the embodiment of each figure, aCCA of the secondary channels may be performed for a PIFS time beforethe backoff counter of the primary channel expires, as described abovein the embodiment of FIG. 18 .

First, FIG. 19(a) illustrates an embodiment in which a wideband PPDU istransmitted according to a contiguous, fixed channel extension method.According to the present method, the CCA obtains up to four CCA resultvalues for each of the P20 channel, S20 channel, S40 channel and S80channel, and only reports information on the first channel determined tobe busy among them. Since the terminal does not perform bandwidthextension from the first channel determined to be busy, the results ofCCA for subsequent channels are not needed. Referring to FIG. 19(a), theS40 channel, which is the first channel determined to be busy as a CCAresult, is reported. Therefore, the terminal transmits a PPDU through a40 MHz band aggregating the P20 channel and the S20 channel According tothe present method, although the burden of report of CCA result value isreduced, there is a disadvantage that the channel utilization is poor.

Next, FIG. 19(b) illustrates an embodiment in which a wideband PPDU istransmitted according to a contiguous, flexible channel extensionmethod. According to the present method, the CCA obtains eight CCAresult values for each channel constituting the 160 MHz band. Accordingto an embodiment, all the obtained eight CCA result values may bereported. However, according to another embodiment, only informationabout the first channels, which are determined to be busy, of both sidesbased on the P20 channel may be reported. Since the terminal does notperform bandwidth extension from the first two channels, which aredetermined to be busy, of the both sides, the results of CCA for thesubsequent channels are not needed. Referring to FIG. 19(b), channelsCH1 and CH5 (not illustrated), which are determined to be busy as a CCAresult, are reported. Therefore, the terminal transmits a PPDU through a60 MHz band including CH2, CH3 and CH4. According to the present method,it is possible to transmit a PPDU having a wider bandwidth composed ofcontiguous channels, but there is a disadvantage that the transmissionbandwidth of the wideband PPDU can be very limited depending on theposition of the secondary channel occupied by OBSS terminals.

Next, FIG. 19(c) illustrates an embodiment in which a wideband PPDU istransmitted according to a non-contiguous, fixed channel extensionmethod. According to the present method, the CCA obtains up to four CCAresult values for each of the P20 channel, S20 channel, S40 channel andS80 channel, and reports information on all the channels determined tobe busy among them. The terminal transmits a PPDU using channels thatare not busy among the reported channels. Referring to FIG. 19(c), theS20 channel and the S80 channel (not illustrated), which are channelsdetermined to be as a CCA result, are reported. Therefore, the terminaltransmits a PPDU through a 60 MHz band including the P20 channel and theS40 channel. According to the present method, the channel utilizationcan be improved compared to the relatively small burden of report of CCAresult values. That is, a maximum of one non-contiguous section occurseven in the 160 MHz bandwidth, and it is possible to transmit thewideband PPDU even when the S20 channel and/or the S40 channel isoccupied by OBSS terminals.

Next, FIG. 19(d) illustrates an embodiment in which a wideband PPDU istransmitted according to a non-contiguous, flexible channel extensionmethod. According to the present method, the CCA obtains eight CCAresult values for each channel constituting the 160 MHz band, andreports all the obtained eight CCA result values. The terminal transmitsa PPDU using channels that are not busy among the reported channels.Referring to FIG. 19(d), channels CH2, CH4, and CH5 (not illustrated) toCH8 (not illustrated), which are determined to be busy as a CCA result,are reported. Therefore, the terminal transmits a PPDU in a 40 MHz bandincluding CH1 and CH3. According to the present method, the channelutilization is the highest, but the burden of report of CCA result valueis large. In addition, a plurality of non-contiguous sections may occurin the transmitted PPDU.

Finally, FIG. 19(e) illustrates an embodiment in which a wideband PPDUis transmitted according to a non-contiguous, limited flexible channelextension method. In the embodiment of the present invention, thelimited flexible channel extension method follows the flexible channelextension method described above. However, in the flexible channelextension method, the band occupied by a transmitted PPDU alwaysconsists of including the predetermined core channels along with the P20channel. In the embodiment of FIG. 19(e), a 40 MHz channel (i.e., P40channel) including a P20 channel and an S20 channel is set as the corechannels. According to the present method, the CCA obtains eight CCAresult values for each channel constituting the 160 MHz band, andreports all the obtained eight CCA result values. The terminal transmitsa PPDU using channels that are not busy among the reported channels. Inthis case, the terminal performs the PPDU transmission only when a PPDUconfiguration is possible through a band including the above-describedcore channels. According to the present method, there are advantagesthat the performance similar to that of the embodiment of FIG. 19(d) isachieved, and the decoding position of the HE-SIG-B can be guaranteedwithin the P40 channel when the P40 channel is set as the core channels.

FIG. 20 illustrates specific embodiments for transmitting a widebandPPDU according to the non-contiguous, fixed channel extension method ofthe embodiment of FIG. 19(c) described above. FIGS. 20(a) and 20(b)illustrate embodiments in which the terminal is equipped with one RFmodule and supports transmission of a PPDU of up to 160 MHz. Inaddition, FIGS. 20(c) and 20(d) illustrate embodiments in which theterminal is equipped with two RF modules and supports transmission of aPPDU of up to 80+80 MHz. It is assumed that the PPDU transmitted in theembodiment of FIG. 20 is an OFDMA-based HE MU PPDU.

First, FIG. 20(a) illustrates a situation in which the terminal attemptsto transmit a PPDU through a bandwidth of 160 MHz but the S40 channel isbusy as a result of CCA. The terminal transmits a PPDU through a 140 MHzband including a P40 channel (i.e., P20 channel+S20 channel) and a S80channel. In this case, the terminal postpones the transmission of dataallocated to the S40 channel among the PPDU configured based on OFDMA.The S40 channel becomes a filtered channel in which no data istransmitted. In the embodiment of FIG. 20(a), the PPDU is transmittedusing a 160 MHz spectral mask. Furthermore, in the S40 channeldetermined to be busy, filtering is performed and no data istransmitted. However, since a 40 MHz spectral mask is not applied to thesignal transmitted through the P40 channel, signals of some resourceunits adjacent to the boundary of the S40 channel may interfere withOBSS signal transmitted through the S40 channel. Therefore, according tothe embodiment of the present invention, in the non-contiguous PPDUtransmission situations, some resource units of a transmission channeladjacent to an unassigned channel may be additionally filtered therebynot transmitting data.

Next, FIG. 20(b) illustrates a situation in which the terminal attemptsto transmit a PPDU through a bandwidth of 80 MHz but the S20 channel isbusy as a result of CCA. The terminal transmits a PPDU through a 60 MHzband including the P20 channel and the S40 channel. In this case, theterminal postpones the transmission of data allocated to the S20 channelamong the PPDU configured based on OFDMA. The S20 channel becomes afiltered channel in which no data is transmitted. In the embodiment ofFIG. 20(b), the PPDU is transmitted using an 80 MHz spectral mask.Furthermore, in the S20 channel determined to be busy, filtering isperformed and no data is transmitted. However, since a 20 MHz spectralmask is not applied to the signal transmitted through the P20 channel,signals of some resource units adjacent to the boundary of the S20channel may interfere with OBSS signal transmitted through the S20channel Therefore, according to the embodiment of the present invention,in the non-contiguous PPDU transmission situations, some resource unitsof a transmission channel adjacent to an unassigned channel may beadditionally filtered thereby not transmitting data.

Next, FIG. 20(c) illustrates a situation in which the terminal attemptsto transmit a PPDU through a bandwidth of 80+80 MHz but the S40 channelis busy as a result of CCA. The terminal transmits a PPDU through theP40 channel (i.e., P20 channel+S20 channel) and the S80 channel,respectively, using two RF modules. In this case, the terminal postponesthe transmission of data allocated to the S40 channel among the PPDUconfigured based on OFDMA. The terminal transmits, by using the first RFmodule, the PPDU to which a 40 MHz spectral mask is applied through theP40 channel. In addition, the terminal transmits, by using the second RFmodule, the PPDU to which an 80 MHz spectral mask is applied through theS80 channel Therefore, in the embodiment of FIG. 20(c), no additionalfiltering of resource units included in the transmission channel isrequired since the transmission channel does not interfere with theunassigned channel S40.

Next, FIG. 20(d) illustrates a situation in which the terminal attemptsto transmit a PPDU through a bandwidth of 80+80 MHz but the S20 channeland the S80 channel are busy as a result of CCA. The terminal transmitsa PPDU through a 60 MHz band including the P20 channel and the S40channel using only the first RF module. In this case, the second RFmodule need not be used, and the operation in the first RF module is asdescribed in the embodiment of FIG. 20(b).

The PPDU transmission methods according to the embodiment of FIG. 20 maybe implemented more easily than the wideband access method according tothe dynamic bandwidth operation described in the embodiment of FIG.18(a). According to the dynamic bandwidth operation, the PPDU should bereconfigured based on the available bandwidth according to the CCAresult before the transmission of the wideband PPDU. In this case, sincethe PPDU is dynamically reconfigured, the implementation complexity isincreased such that the length of the PPDU should be limited to thelength of the allocated TXOP. However, according to the embodiment ofFIG. 20 , the implementation is relatively easy since the terminalconfigures an OFDMA-based PPDU in advance and then transmits only thedata allocated to the idle channels and filters the data allocated tothe remaining busy channels.

Hereinafter, transmission sequences of a non-contiguous PPDU accordingto embodiments of the present invention will be described with referenceto FIGS. 21 to 23 . In the embodiments of FIGS. 21 to 23 , CH1 to CH4refer to respective 20 MHz channels constituting the 80 MHz bandwidth.In addition, in the embodiments of FIGS. 21 and 22 , it is designatedthat CH3 is a P20 channel, CH4 is an S20 channel, and CH1 and CH2 are anS40 channel, respectively. In the embodiments of FIGS. 21 to 23 ,duplicative descriptions of parts which are the same or corresponding asthose of the above-described embodiments of FIGS. 8 and 9 will beomitted.

FIG. 21 illustrates a transmission sequence of a non-contiguous PPDUaccording to an embodiment of the present invention. FIGS. 21(a) and21(b) illustrate downlink transmission sequences of a non-contiguousPPDU, and FIGS. 21(c) and 21(d) illustrate uplink transmission sequencesof a non-contiguous PPDU.

First, FIG. 21(a) illustrates an embodiment in which an AP performs aCCA for a DL-MU transmission process but the S20 channel is busy. The APtransmits an MU-RTS frame through the P20 channel and the S40 channelwhich are idle. STAs receiving the MU-RTS frame from the AP transmit asCTS frame through the corresponding channel. The AP transmits a DL MUPPDU through the channel on which the sCTS frame is received. In thiscase, the MU-RTS frame should indicate non-contiguous channel allocationinformation, that is, the P20 channel and the S40 channel (or theunassigned S20 channel). According to an embodiment, the MU-RTS framemay signal the non-contiguous channel allocation information via abandwidth field, an RA field, or a combination thereof.

Next, FIG. 21(b) illustrates an embodiment in which an AP transmits anMU-RTS frame through an idle P80 channel (i.e., P20 channel+S20channel+S40 channel), but a sCTS frame of STAs is not received throughthe S20 channel. The AP transmits a DL MU PPDU through the P20 channeland the S40 channel on which the sCTS frame is received. In this case,the MU-RTS frame should indicate channel allocation information, i.e.,the P80 channel. The channel allocation information may be signaled viaa separate bandwidth field. In addition, the DL MU PPDU should indicatenon-contiguous channel allocation information through which thecorresponding PPDU is transmitted, that is, the P20 channel and the S40channel (or the unassigned S20 channel). The non-contiguous channelallocation information may be signaled via a bandwidth field, an RAfield, or a combination thereof.

Next, FIG. 21(c) illustrates an embodiment in which an AP performs a CCAfor a UL-MU transmission process but the S20 channel is busy. The APtransmits a trigger frame through the P20 channel and the S40 channelwhich are idle. STAs receiving the trigger frame from the AP transmit aUL MU PPDU through designated channel(s). In this case, the triggerframe should indicate non-contiguous channel allocation information,that is, the P20 channel and the S40 channel (or the unassigned S20channel), for the UL MU PPDU transmission of STAs. In addition, thetrigger frame should not assign the busy S20 channel to the uplinktransmission of the STAs. According to an embodiment, the trigger framemay signal the non-contiguous channel allocation information via abandwidth field, an RA field, or a combination thereof.

Finally, FIG. 21(d) illustrates a sequence in which an AP transmits atrigger frame through an idle P80 channel and STAs transmit a UL MU PPDUin response thereto. In this case, among the STAs receiving the triggerframe, STAs allocated to the S20 channel do not perform a transmissionfor the reason that the corresponding channel is detected as busy or aNAV has been set.

FIG. 22 illustrates a transmission sequence of a non-contiguous PPDUaccording to another embodiment of the present invention. FIGS. 22(a)and 22(b) illustrate downlink transmission sequences of a non-contiguousPPDU, and FIGS. 22(c) and 22(d) illustrate uplink transmission sequencesof a non-contiguous PPDU. In the embodiment of FIG. 22 and the followingembodiments, an S40A channel refers to the first 20 MHz channel (i.e.,CH1) that constitutes the S40 channel, and an S40B channel refers to thesecond 20 MHz channel (i.e., CH2) that constitutes the S40 channel.

First, FIG. 22(a) illustrates an embodiment in which an AP performs aCCA for a DL-MU transmission process but the S40B channel is busy. TheAP transmits an MU-RTS frame through the P40 channel and the S40Achannel which are idle. STAs receiving the MU-RTS frame from the APtransmit a sCTS frame through the corresponding channel. In this case,the MU-RTS frame should indicate the non-contiguous channel allocationinformation, that is, the P40 channel and the S40A channel (or theunassigned S40B channel). According to an embodiment, the MU-RTS framemay signal the non-contiguous channel allocation information via abandwidth field, an RA field, or a combination thereof. Meanwhile, inthe embodiment of FIG. 22(a), among the STAs that have received theMU-RTS, STAs indicated to transmit the sCTS frame through the S40Achannel do not transmit the sCTS for the reason that the correspondingchannel is detected as busy or a NAV has been set. In this case, the APtransmits a DL MU PPDU only through the P20 channel and the S20 channelon which the sCTS is received.

Next, FIG. 22(b) illustrates an embodiment in which an AP transmits anMU-RTS frame through an idle P80 channel, but the sCTS frame of the STAsis not received on the S40A channel. The AP transmits a DL MU PPDUthrough the P40 channel and the S40B channel on which the sCTS frame isreceived. In this case, the MU-RTS frame should indicate the P80 channelas channel allocation information, and the DL MU PPDU should indicatenon-contiguous channel allocation information, that is, the P40 channeland the S40B channel (or the unassigned S40A channel). The signalingmethod of the channel allocation information is as described above inthe embodiment of FIG. 21(b).

Next, FIG. 22(c) illustrates an embodiment in which an AP performs a CCAfor the UL-MU transmission process but the S40B channel is busy. The APtransmits a trigger frame through the P40 channel and the S40A channelwhich are idle. In this case, the trigger frame indicates non-contiguouschannel allocation information, i.e., the P40 channel and the S40Achannel (or the unassigned S40B channel), for the UL MU PPDUtransmission of STAs. The trigger frame may signal the non-contiguouschannel allocation information via a bandwidth field, an RA field, or acombination thereof. Meanwhile, among the STAs receiving the triggerframe in the embodiment of FIG. 22(c), STAs indicated to transmit uplinkdata through the S20 channel do not transmit uplink data for the reasonthat the channel is detected as busy or a NAV has been set. Thus, the APmay receive a UL MU PPDU through a band that is equal to or narrowerthan the band on which the trigger frame has been transmitted.

Finally, FIG. 22(d) illustrates an embodiment in which an AP transmits atrigger frame through an idle P80 channel, but STAs allocated to the S20channel do not perform a transmission for the reason that thecorresponding channel is detected as busy or a NAV has been set.

FIG. 23 illustrates an embodiment of an ACK frame transmission method ina PPDU transmission sequence. In the embodiment of FIG. 23 , it isdesignated that CH1 is a P20 channel, CH2 is an S20 channel, and CH3 andCH4 are an S40 channel, respectively.

First, FIG. 23(a) illustrates an embodiment of an ACK frame transmissionmethod in a transmission sequence of a contiguous PPDU. The AP transmitsa DL MU PPDU using a contiguous bandwidth of 80 MHz, and the receivingSTAs transmit a UL MU response. In this case, the STAs transmit animmediate uplink response according to scheduling information includedin the A-MPDU of the received DL MU PPDU. The scheduling information isobtained from a trigger frame included in the A-MPDU or a UL MU responsescheduling field included in a MAC header of a specific MPDUconstituting the A-MPDU. Also, the uplink response transmitted by theSTAs includes uplink ACK, uplink data, and the like. According to anembodiment of the present invention, the scheduling information, thatis, the resource units through which the STAs perform the UL MU responsemay be indicated via a separate resource unit allocation (RA) field.FIG. 23(d) illustrates an embodiment in which resource units for uplinktransmission are assigned through the separate RA field.

Referring to FIG. 23(d), the RA field consists of 8 bits in total, andthe first bit indicates whether the corresponding resource unit(s) islocated at the primary 80 MHz or the secondary 80 MHz. The remaining 7bits of the RA field indicate resource unit allocation within thecorresponding 80 MHz band. That is, a size of a predetermined resourceunit and a placement of the corresponding resource unit are indicatedaccording to the index value of the RA field. In the embodiment of FIG.23(a), STAs may transmit an uplink ACK through a designated resourceunit within an 80 MHz band on which the DL MU PPDU has been transmitted.

However, as in the embodiment of FIG. 23(b), a problem may occur in aresource unit allocation for ACK frame transmission in the transmissionsequence of a non-contiguous PPDU. More specifically, as illustrated inFIG. 23(b), when there is no constraint on the resource unit throughwhich the ACK frame for the non-contiguous PPDU is transmitted, anuplink ACK may be transmitted through a channel (i.e., CH3) which is notused for the DL MU PPDU transmission. This may cause interference withOBSS signal transmitted through CH3. As described above in theembodiment of FIGS. 21 and 22 , the transmission of the non-contiguousPPDU may be determined immediately before the PPDU transmissionaccording to the CCA results for multiple channels. Thus, it may beimpossible to adjust the scheduling information for the resource unitson which the UL MU response of the STAs is to be performed, immediatelybefore the transmission of the non-contiguous PPDU.

In order to solve such a problem, as illustrated in FIG. 23(c), aconstraint may be applied to resource unit allocation for the ACK frametransmission. According to the embodiment of the present invention, STAsreceiving the DL MU PPDU from the AP transmit an uplink ACK within a 20MHz channel where the resource unit on which the corresponding PPDU hasbeen received is located. If a STA receives a DL MU PPDU with MU-MIMOthrough a 40 MHz channel or an 80 MHz channel, the STA may transmit anuplink ACK within the corresponding 40 MHz channel or 80 MHz channel.The AP signals such scheduling information for the ACK frametransmission of STAs.

Referring to FIG. 23(c), the AP transmits a DL MU PPDU through the P40channel and the S40B channel. In this case, STAs receiving the PPDUthrough the S40B channel (i.e., a 20 MHz channel) transmit an ACK framewithin the S40B channel. If a full bandwidth MU-MIMO transmission isperformed on the P40 channel (i.e., a 40 MHz channel), STAs may transmitan ACK frame within the P40 channel. However, if an OFDMA transmissionis performed on the P40 channel, STAs transmit an ACK frame within a 20MHz channel where a resource unit on which the PPDU has been received islocated.

Meanwhile, although an embodiment of the ACK frame transmission methodin the DL-MU transmission process has been described with reference toFIG. 23 , the present invention is not limited thereto and may besimilarly applied to the UL-MU transmission process. That is, inresponse to a trigger frame of the AP, STAs may transmit an HETrigger-based PPDU through the allocated resource unit. The AP transmitsa downlink ACK in response to the HE Trigger-based PPDU(s) transmittedby the STAs. In this case, the AP transmits an ACK frame for each STAwithin a 20 MHz channel where a resource unit on which the correspondingSTA has transmitted the HE Trigger-based PPDU is located. Therefore, aSTA that has transmitted the HE Trigger-based PPDU may receive the ACKframe within the 20 MHz channel where the resource unit on which thePPDU has been transmitted is located.

FIG. 24 illustrates a method of setting a TXOP of an MU transmissionprocess as an additional embodiment of the present invention. Accordingto the embodiment of the present invention, a TXOP may be set using bothof TXOP information of the HE-SIG-A and duration field information ofthe MAC header.

FIG. 24(a) illustrates an embodiment of an arrangement situation ofterminals adjacent to a specific BSS. In the embodiment of FIG. 24(a),an AP communicates with STA1 and STA2, and hidden nodes L1, H1, L2 andH2 are present based on a specific terminal. Here, L1 and L2 refer to alegacy STA, respectively, and H1 and H2 refer to a non-legacy STA,respectively. L1 and H1 can sense messages of the AP, but cannot receivemessages of STA1 and STA2. Thus, L1 and H1 may interfere with the APwhen the AP receives messages from STA1 and STA2. On the other hand, L2and H2 can sense messages of STA2, but cannot receive messages of AP.Thus, L2 and H2 may interfere with STA2 when STA2 receives messages fromthe AP. Therefore, in order to protect the MU transmission process, aNAV should be set in the hidden nodes L1, H1, L2 and H2.

FIG. 24(b) illustrates a method in which a TXOP of a UL-MU transmissionprocess is set in the arrangement situation of the terminals of FIG.24(a). First, the AP transmits an MU-RTS frame on multiple channels (forexample, 40 MHz). In this case, the legacy preambles such as L-STF,L-LTF, and L-SIG are transmitted in duplicate for each 20 MHz channel.If the MU-RTS frame is transmitted in the legacy format, H1 and L1 whichhave received the MU-RTS frame set a NAV based on a duration field of aMAC header of the MU-RTS frame.

Next, STA1 and STA2 receiving the MU-RTS frame transmit a sCTS frameafter a SIFS time. In this case, the sCTS frame may be transmitted inunits of 20 MHz channel STAs receiving the MU-RTS may restrict atransmission of the sCTS frame considering a NAV already set in thecorresponding terminal. H2 and L2 receiving the sCTS frame set a NAVbased on a duration field of a MAC header of the sCTS frame.

The AP receiving the sCTS frame may transmit a trigger frame in HE PPDUformat. In this case, in the trigger frame, the TXOP duration field ofthe HE-SIG-A and the duration field of the MAC header indicate durationinformation, respectively. The two duration fields may have differentbit configurations with each other. For example, the number of bits inthe TXOP duration field may be less than the number of bits in theduration field of the MAC header. In this case, the setting method ofeach duration field and/or the interpretation method of each durationfield should be determined in order to set a correct NAV of theneighboring terminals.

According to an embodiment of the present invention, when the TXOPduration field consists of t bits and the duration field of the MACheader consists of m bits (where t<m), the value of the duration fieldof the MAC header may be set to not exceed the value of the TXOPduration field. For example, if the TXOP duration field consists of 12bits and the duration field of the MAC header consists of 15 bits, thevalue of the duration field of the MAC header shall not exceed themaximum value that the TXOP duration field can represent, that is,2{circumflex over ( )}12=4096 us. In this case, the interpretation ofeach duration field may be performed in the same way.

According to another embodiment of the present invention, when thenumber of bits in the TXOP duration field and the number of bits in theduration field of the MAC header are different from each other, apredetermined scaling factor may be multiplied when performing aninterpretation of any one of the above fields. For example, if the TXOPduration field consists of 12 bits and the duration field of the MACheader consists of 15 bits, the value of the TXOP duration field may beused after a scaling factor 8 is multiplied. In this way, by using thepredetermined scaling factor, duration information indicated by theduration fields of different number of bits may have similar range.

However, if the value of the TXOP duration field is used after thescaling factor 8 is multiplied, duration information obtained from thetwo duration fields may have a difference of up to 7 us. According to anembodiment of the present invention, a STA that has interpreted all ofthe two duration fields may set a NAV based on the duration field of theMAC header having a larger number of bits. However, a STA which can onlyinterpret the TXOP duration field of the HE-SIG-A among the two durationfields sets a NAV based on the TXOP duration field. In preparation forthis situation, the value of the TXOP duration field in a PPDU may beset to a value which is larger or smaller than the value of the durationfield of the MAC header by the maximum offset (e.g., 7 us).

In the embodiment of FIG. 24(b), since H1 receiving the trigger framecan interpret both the TXOP duration field of the HE-SIG-A and theduration field of the MAC header, it may update a NAV using both the twofields. However, L1 cannot update a NAV because it cannot interpret thenon-legacy preamble and MPDU of the HE PPDU.

On the other hand, STA1 and STA2 receiving the trigger frame transmit anHE Trigger-based PPDU. In this case, since H2 receiving the HETrigger-based PPDU can interpret both the duration field of the HE-SIG-ATXOP and the duration field of the MAC header, it may update a NAV usingboth the two fields. However, L2 cannot update a NAV because it cannotinterpret the non-legacy preamble and MPDU of the HE Trigger-based PPDU.

FIGS. 25 to 31 illustrate methods of signaling non-contiguous channelallocation information according to various embodiments of the presentinvention. In the embodiment of the present invention, non-contiguouschannel allocation refers to channel allocation in which a band occupiedby the transmitted packet (i.e., PPDU) includes at least onenon-contiguous channel (or non-contiguous resource unit). However, afull bandwidth 80+80 MHz channel is regarded as a contiguous channellike a full bandwidth 160 MHz channel. Thus, a non-contiguous channel(or non-contiguous PPDU) in the embodiments of the present invention mayrefer to non-contiguous channels except for the full bandwidth 80+80 MHzchannel. In the embodiments of FIGS. 25 to 31 , channel A to channel Drefer to each 20 MHz channel through which an 80 MHz PPDU istransmitted. In this case, it is designated that channel A is a P20channel, channel B is an S20 channel, and channel C and channel D are anS40 channel, respectively. Also, in each embodiment, an S40A channel mayrefer to channel C, and an S40B channel may refer to channel D.

In the embodiment of the present invention, a transmitter (e.g., an AP)signals non-contiguous channel allocation information throughembodiments illustrated in each figure or combinations thereof. Thetransmitter may perform a CCA of multiple channels for a wideband packettransmission. In this case, the wideband may refer to a band having atotal bandwidth of 40 MHz or more, but the present invention is notlimited thereto. The transmitter transmits a packet through at least onechannel which is idle based on the result of performing the CCA ofmultiple channels. In this case, when the packet is transmitted througha non-contiguous channel, the transmitter signals non-contiguous channelallocation information via a non-legacy preamble of the packet. As such,the transmitter transmits a wireless packet in which non-contiguouschannel allocation information is signaled. A receiver (e.g., a STA)receives the wireless packet and obtains the non-contiguous channelallocation information from the received packet. The receiver decodesthe received packet based on the obtained non-contiguous channelallocation information. In this case, the received packet may be an HEMU PPDU, but the present invention is not limited thereto.

FIG. 25 illustrates a signaling method of non-contiguous channelallocation information according to an embodiment of the presentinvention. In the embodiment of FIG. 25 , the AP performs a CCA ofchannel A to channel D to transmit a DL MU PPDU through a totalbandwidth of 80 MHz, and the S40B channel is determined to be busy. TheAP transmits a PPDU through the P40 channel and the S40A channel whichare idle. The AP performs nulling of data tones of the busy S40B channeland does not transmit any signal. In this case, non-contiguous channelallocation information, that is, allocation information of the P40channel and the S40A channel (or information of the unassigned S40Bchannel) should be signaled on the transmitted PPDU.

First, the non-contiguous channel allocation information may beindicated via the bandwidth field of the HE-SIG-A. The bandwidth fieldmay indicate specific non-contiguous channel allocation informationthrough a predetermined index. According to an embodiment, the bandwidthfield may explicitly indicate specific non-contiguous channel allocationinformation. Therefore, the allocation information of the P40 channeland the S40A channel may be indicated via the bandwidth field.

Also, the non-contiguous channel allocation information may be indicatedvia the RA field of the HE-SIG-B. The RA field may indicate a specificresource unit not assigned to a user through a predetermined index. Forexample, the RA field may indicate that a resource unit of a multiple ofa 20 MHz channel, i.e. 242-tone, 484-tone or 996-tone, is not assignedto a user. Data transmission is not performed in an empty resource unitindicated by a predetermined index value.

Also, the non-contiguous channel allocation information may be indicatedby carrying a null STA ID in a specific user field of the HE-SIG-B. Thatis, a predetermined null STA ID is contained in a user fieldcorresponding to an unassigned resource unit in which data is nottransmitted. Therefore, no STA receives data through the unassignedresource unit.

FIG. 26 illustrates a method of signaling non-contiguous channelallocation information via the bandwidth field of the HE-SIG-A accordingto an embodiment of the present invention. The bandwidth field of an HEMU PPDU may indicate predetermined non-contiguous channel bandwidths inaddition to the contiguous channel bandwidths of 20 MHz, 40 MHz, 80 MHz,and 160 MHz (including 80+80 MHz). If the bandwidth field indicates apredetermined non-contiguous channel bandwidth, additional allocationinformation of the non-contiguous channel may be indicated via asubfield of the HE-SIG-B.

As described above, the HE-SIG-B may consist of a maximum of two contentchannels, i.e., the HE-SIG-B content channel 1 and the HE-SIG-B contentchannel 2 in units of 20 MHz. Each HE-SIG-B content channel in the totalband is arranged in order of the physical frequency band. That is, theHE-SIG-B content channel 1 is transmitted in the lowest frequency band,and the HE-SIG-B content channel 2 is transmitted in the next higherfrequency band. Such a content channel configuration is then duplicatedthrough content duplication in the next higher frequency bands. In theembodiment of FIG. 26 , the HE-SIG-B content channel 1 signals resourceunit allocation information of channel A and channel C, and the HE-SIG-Bcontent channel 2 signals resource unit allocation information ofchannel B and channel D. The HE-SIG-B content channel 1 is transmittedthrough channel A and channel C. However, since a PPDU transmission isnot performed in channel D, the HE-SIG-B content channel 2 istransmitted only through channel B. In this case, the HE-SIG-B contentchannel 2 transmitted through the channel B may indicate that channel Dis not used.

FIG. 27 illustrates a method of signaling non-contiguous channelallocation information via the RA field of the HE-SIG-B according to anembodiment of the present invention. As described above, the RA fieldconsists in units of 8 bits, and indexes the sizes of the resource unitsconstituting the specific bandwidth and their placement in the frequencydomain. Further, the RA field may indicate the number of users in eachresource unit. In this case, the RA field may indicate a specificresource unit (i.e., an unassigned RU) not assigned to a user through apredetermined index. According to an embodiment, the specific resourceunit includes a resource unit (RU) having a bandwidth of a multiple of a20 MHz channel, i.e., 242-tone RU, 484-tone RU, 996-tone RU, and thelike. Data transmission is not performed in the unassigned RU indicatedby the index value.

As shown in FIG. 27(a), when the total bandwidth through which a PPDU istransmitted is 80 MHz, two RA fields are transmitted in each HE-SIG-Bcontent channel. That is, the first RA field (i.e., 8 bits) of theHE-SIG-B content channel 1 signals resource unit allocation informationof channel A, and the second RA field (i.e., 8 bits) of the HE-SIG-Bcontent channel 1 signals resource unit allocation information ofchannel C. Similarly, the first RA field (i.e., 8 bits) of the HE-SIG-Bcontent channel 2 signals resource unit allocation information ofchannel B, and the second RA field (i.e., 8 bits) of the HE-SIG-Bcontent channel 2 signals resource unit allocation information ofchannel D. If the channel D is busy as in the embodiment of FIG. 27(a),the HE-SIG-B content channel 2 is transmitted only through channel B,and the HE-SIG-B content channel 1 is transmitted through channel A andchannel C. In this case, specific embodiments of signaling through theRA field of the HE-SIG-B that the channel D is not assigned to a userwill be described with reference to FIGS. 27(b) to 27(d).

First, according to an embodiment of the present invention, as shown inFIG. 27(b), the RA field corresponding to the unassigned 20 MHz channel,that is, the second RA field of the HE-SIG-B content channel 2 mayindicate a nulling of 242-tone RU. However, the second RA field of theHE-SIG-B content channel 1 indicates a 242-tone RU or indicates RUspartitioned into smaller sizes according to resource allocationinformation of channel C. As above, the RA field may perform independentand explicit signaling for each channel Therefore, the RA fieldcorresponding to the unassigned channel D indicates that thecorresponding resource unit is not assigned to a user (i.e. nulling).

Next, according to another embodiment of the present invention, as shownin FIG. 27(c), the RA field corresponding to the unassigned 20 MHzchannel, that is, the second RA field of the HE-SIG-B content channel 2may indicate a nulling of 484-tone RU. However, since the second RAfield of the HE-SIG-B content channel 1 indicates resource allocationinformation of the channel C, it can be identified that the unassignedchannel is channel D of a 20 MHz bandwidth.

Next, according to yet another embodiment of the present invention, asshown in FIG. 27(d), the RA field corresponding to the unassigned 20 MHzchannel may indicate a general nulling rather than a nulling of resourceunits of a specific bandwidth such as 242-tone RU, 484-tone RU, 996-toneRU, and the like. In this case, the nulling indicated by the RA fieldmay implicitly be interpreted as a nulling of 242-tone RU (i.e., 20 MHzchannel), and information of resource units assigned to users may beobtained via another RA field.

As such, when the RA field indicates that a specific resource unit isnot assigned to a user, a user specific field corresponding to theresource unit is not transmitted. Thus, as shown in FIG. 27(a), theHE-SIG-B content channel 2 signaling resource unit allocationinformation of channel D does not carry the user specific field 410corresponding to channel D.

FIG. 28 illustrates a method of signaling non-contiguous channelallocation information via the user field of the HE-SIG-B according toan embodiment of the present invention. As described above, thenon-contiguous channel allocation information may be indicated bycarrying a null STA ID in a specific user field of the HE-SIG-B. The RAfield of the HE-SIG-B may indicate resource allocation informationcorresponding to an unassigned resource unit, and a predetermined nullSTA ID may be contained in a user field corresponding to the unassignedresource unit.

If channel D is not used as in the embodiment of FIG. 28 , the second RAfield of the HE-SIG-B content channel 2 corresponding to channel Dindicates a 242-tone resource unit and one user. Thus, the second RAfield indicates that one user field 420 is carried for the corresponding242-tone resource unit. The user specific field of the HE-SIG-B contentchannel 2 carries user fields of the total number of users indicated inthe first RA field and the second RA field of the HE-SIG-B contentchannel 2. In this case, a predetermined null STA ID is contained in theuser field 420 corresponding to the unassigned channel i.e., channel D.According to the embodiment of the present invention, the null STA IDmay be an unassigned AID among AIDs from 1 to 2007 of the correspondingBSS, a reserved AID (e.g., 2046) which has a value greater than 2007, ora predetermined AID among AIDs from 1 to 2007. When a null STA ID iscontained in the user field 420, a non-contiguous channel allocation maybe performed since no STA in the BSS receives data through thecorresponding resource unit.

FIG. 29 illustrates a signaling method of non-contiguous channelallocation information according to a further embodiment of the presentinvention. According to the embodiment of FIG. 29 , whether a user isallocated to a center 26-tone resource unit 502 may be signaled via auser field 422 of the HE-SIG-B. In an embodiment of the presentinvention, the center 26-tone resource unit (RU) refers to the RU 502located at the center of an 80 MHz bandwidth. As described below,whether or not a user is allocated to the center 26-tone RU 502 may bedetermined according to various embodiments.

According to the embodiment of the present invention, the user field 422corresponding to the center 26-tone RU 502 may be carried in theHE-SIG-B content channel 1 as shown in FIG. 29 . In this case, the userfield 422 may be carried as the last user field in the HE-SIG-B contentchannel 1. According to an embodiment of the present invention, whethera user is allocated to the center 26-tone RU 502 may be indicated via aSTA ID contained in the corresponding user field 422. That is, when thecenter 26-tone RU 502 is not assigned to a user, a null STA ID may becontained in the corresponding user field 422. A specific embodiment ofthe null STA ID is as described in the embodiment of FIG. 28 . However,when the center 26-tone RU 502 is assigned to a particular user, a STAID of the particular user may be contained in the corresponding userfield 422.

FIG. 30 illustrates a signaling method of non-contiguous channelallocation information according to a further embodiment of the presentinvention. According to the embodiment of FIG. 30 , whether or not anarbitrary resource unit 504 is assigned to a user may be signaled via auser field 424 of the HE-SIG-B. An OFDMA-based DL MU PPDU includesresource units up to nine within a 20 MHz bandwidth, each of whichconsists of 26 subcarriers. In this case, data may be transmittedthrough only eight resource units among the nine RUs, and data may notbe transmitted through one resource unit. In addition, a PPDU in a totalbandwidth of 80 MHz may include resource units up to 37, some of whichmay not transmit data. As such, when some of the resource unitsconstituting the total bandwidth are not assigned to a user, a method ofindicating the unassigned resource unit is required.

According to an embodiment of the present invention, such non-contiguouschannel allocation information may be indicated via the RA field and theuser field of the HE-SIG-B. As described above, the RA field indicatesinformation on the arrangement of resource units constituting a specificbandwidth and the number of users. The user fields corresponding to eachresource unit are carried in the user specific field of the HE-SIG-Baccording to the order of resource unit allocation indicated by the RAfield. According to the embodiment of the present invention, theunassigned resource unit may be indicated via a null STA ID contained inthe user field 424 corresponding to the specific resource unit 504 inthe resource unit arrangement indicated by the RA field. In this case,the unassigned resource unit that can be indicated includes at least oneof 26-tone RU, 52-tone RU, and 106-tone RU, but the present invention isnot limited thereto. That is, as described in FIG. 28 , the unassignedresource unit that can be indicated via the null STA ID may include242-tone RU, 484-tone RU, and 996-tone RU of a 20 MHz bandwidth or more.A specific embodiment of the null STA ID is as described in theembodiment of FIG. 28 .

Next, with reference to FIG. 31 , matters that can be considered whensignaling the non-contiguous channel allocation information will bedescribed. The HE MU PPDU performs signaling through the HE-SIG-A andthe HE-SIG-B. The HE-SIG-A carries overall information includingbandwidth information of the PPDU, and the HE-SIG-B carries informationfor a simultaneous multi-user transmission. In a total PPDU bandwidth of40 MHz or more, the HE-SIG-B may consist of HE-SIG-B content channel 1and HE-SIG-B content channel 2. According to the embodiment of thepresent invention, when a transmission of a non-contiguous PPDU isperformed, the following matters can be considered.

First, all types of non-contiguous PPDUs should assign the P20 channel.That is, the non-contiguous PPDU may include one or more unassignedchannels (or unassigned resource units), but the P20 channel should beassigned to one or more users.

Second, the HE-SIG-A of the non-contiguous PPDU should be able toindicate channel information on which the content channel(s) of theHE-SIG-B of the PPDU is transmitted. Referring to FIG. 31(a), channelsof an 80 MHz bandwidth consist of channel A, channel B, channel C andchannel D in an increasing order of the frequency, and a non-contiguousPPDU may be transmitted through channel A, channel B and channel Dexcept a busy channel C. In this case, the HE-SIG-B content channel 1 istransmitted through channel A, and the HE-SIG-B content channel 2 istransmitted through channel B and channel D. In this case, the bandwidthfield of the HE-SIG-A may indicate information about at least whichchannel each of the HE-SIG-B content channels of the corresponding PPDUis transmitted through. As described below, the bandwidth field of theHE-SIG-A may index puncturing of the S20 channel, and puncturing of atleast one of two channels of the S40 channel, respectively. When thebandwidth field indicates puncturing of the S20 channel, at least onecontent channel of the two HE-SIG-B content channels may be transmittedthrough the S40 channel. On the other hand, when the bandwidth fieldindicates puncturing of at least one of two 20 MHz channels in the S40channel as shown in FIG. 31(a), all of the two HE-SIG-B content channelsmay be transmitted through at least the P40 channel.

Finally, the HE-SIG-A may explicitly or implicitly indicate the sizeinformation of the common block field of the HE-SIG-B in thecorresponding PPDU. As illustrated in FIG. 31(b), the HE-SIG-B consistsof a common block field 430 and a user specific field 440, and thecommon block field 430 includes an RA field. When a total bandwidth ofthe PPDU is 20 MHz or 40 MHz, each HE-SIG-B content channel carries oneRA field. However, when the total bandwidth of the PPDU is 80 MHz or 160MHz (80+80 MHz), each HE-SIG-B content channel may carry multiple RAfields 432 as shown in FIG. 31(c). That is, when the total bandwidth ofthe PPDU is 80 MHz, each HE-SIG-B content channel carries two RA fields432. Furthermore, when the total bandwidth of the PPDU is 160 MHz (or80+80 MHz), each HE-SIG-B content channel carries four RA fields 432.Therefore, the number of RA fields 432 carried in the common block field430 of the HE-SIG-B varies according to the information indicated by thebandwidth field 452 of the HE-SIG-A. The bandwidth field 452 of theHE-SIG-A may indicate the number of RA fields 432 carried in the commonblock field 430 of the HE-SIG-B, thereby explicitly or implicitlyindicating the size information of the common block field 430.

According to the embodiment of the present invention, the non-contiguouschannel allocation information may be indicated via any one ofsubfield(s) of the HE-SIG-A, subfield(s) of the HE-SIG-B, and acombination thereof. The non-contiguous channel allocation informationmay be signaled as the following specific embodiments.

First, the non-contiguous channel allocation information may be signaledsolely via subfield(s) of the HE-SIG-A. The bandwidth field 452 of theHE-SIG-A may indicate specific non-contiguous channel allocationinformation through a predetermined index. When the non-contiguouschannel allocation information is signaled through the subfield of theHE-SIG-A, the receiver may promptly obtain the entire configurationinformation of the PPDU. In addition, the additional signaling overheadthrough the HE-SIG-B is reduced when the non-contiguous channelallocation information is signaled via only the subfield of theHE-SIG-A.

However, due to the limitation of the available number of bits in theHE-SIG-A, various non-contiguous channel allocation information may notbe signaled. Thus, according to an embodiment of the present invention,the bandwidth field 452 may explicitly indicate only some non-contiguouschannel allocation information among the various options of thenon-contiguous channel allocation. According to another embodiment ofthe present invention, some subfields of the HE-SIG-A that areunnecessary when non-contiguous channel allocation is performed may beused for additional signaling of the non-contiguous channel allocationinformation. For example, when the non-contiguous channel allocation isperformed, a SIG-B compression field 454 indicating whether to use thefull bandwidth MU-MIMO is unnecessary. Thus, when the non-contiguouschannel allocation is performed, the SIG-B compression field 454 may beused for other purposes. For example, the HE-SIG-A may indicatenon-contiguous channel allocation information using both the bandwidthfield 452 and the SIG-B compression field.

Next, the non-contiguous channel allocation information may be signaledsolely via subfield(s) of the HE-SIG-B. In this case, the bandwidthfield of the HE-SIG-A indicates the existing contiguous bandwidths, andinformation of the unassigned channel (or unassigned resource unit) maybe indicated via the RA field 432 and/or the user field of the HE-SIG-B.In this case, the signaling overhead of the HE-SIG-A may be reduced, butthe signaling overhead of the HE-SIG-B may increase.

Finally, the non-contiguous channel allocation information may besignaled via a combination of subfield(s) of the HE-SIG-A andsubfield(s) of the HE-SIG-B. The subfield(s) of the HE-SIG-A may signalat least a portion of the non-contiguous channel allocation information,and the subfield(s) of the HE-SIG-B may signal the remaininginformation. According to an embodiment, a subfield of the HE-SIG-A maysignal the detailed information of the PPDU configuration of the P80channel and information on whether to transmit the S80 channel. If thesubfield of the HE-SIG-A indicates transmission of the S80 channel, thesubfield(s) of the HE-SIG-B may signal the detailed information of thePPDU configuration of the S80 channel According to another embodiment,the subfield of the HE-SIG-A may signal channel information on which theHE-SIG-B content channel(s) of the corresponding PPDU is transmitted andsize information of the common block field 430. The subfield(s) of theHE-SIG-B signal additional information of the corresponding PPDUconfiguration. According to yet another embodiment, when thetransmission band of the non-contiguous PPDU always includes the P40channel, the size information of the common block field 430 of theHE-SIG-B may be signaled via the subfield of the HE-SIG-A.

FIGS. 32 to 34 illustrate non-contiguous channel allocation methodsaccording to various embodiments of the present invention. Thenon-contiguous channel allocation information according to theembodiments of FIGS. 32-34 may be signaled via a combination of at leastone of the various embodiments described in FIGS. 25 to 31 .

FIG. 32 illustrates a non-contiguous channel allocation method accordingto an embodiment of the present invention. According to an embodiment ofthe present invention, the non-contiguous channel allocation informationmay be signaled solely via the bandwidth field of the HE-SIG-A. FIG. 32illustrates an embodiment in which the P40 channel is always allocatedin a non-contiguous PPDU to fix the decoding position of the HE-SIG-Bcontent channel. In this case, both the HE-SIG-B content channel 1 andthe HE-SIG-B content channel 2 may be transmitted through at least theP40 channel. In the embodiment of 32 and the following embodiments, anS80A channel, an S80B channel, an S80C channel, and an S80D channelrefer to the first, second, third and fourth 20 MHz channels,respectively, constituting the S80 channel.

The bandwidth field of the HE-SIG-A may basically index information offour contiguous channels 510, that is, 20 MHz, 40 MHz, 80 MHz and 160MHz (including 80+80 MHz), respectively. When the bandwidth fieldconsists of 3 bits, the bandwidth field may index information of fouradditional non-contiguous channels 520. First, the bandwidth field mayindex each puncturing of one of two 20 MHz channels in the S40 channel.In addition, the bandwidth field may index whether the S80 channel isallocated, in combination with the configuration of the S40 channelTherefore, the bandwidth field may index four non-contiguous channelconfigurations in total by combining two configurations of P40+S40A andP40+S40B in the P80 channel and two configurations according to whetherthe S80 channel is allocated.

Next, when the bandwidth field consists of 4 bits, the bandwidth fieldmay additionally index information of eight non-contiguous channels 530in addition to the information of the four non-contiguous channels 520.First, the bandwidth field may index each puncturing of two 20 MHzchannels in the S40 channel. In addition, the bandwidth field may indexinformation of six non-contiguous channels in the S80 channel incombination with the configuration of the S40 channel. In this case, theinformation of the six non-contiguous channels includes whether the S80channel is allocated, and may include four puncturing options that mayallocate a contiguous 40 MHz band as shown in FIG. 32 .

FIG. 33 illustrates a non-contiguous channel allocation method accordingto another embodiment of the present invention. According to theembodiment of FIG. 33 , the location where at least one of the HE-SIG-Bcontent channels is transmitted may be variable. In this case, thereceiver should be able to variably set the decoding channel forreceiving the HE-SIG-B content channel. In the embodiment of FIG. 33 ,it is assumed that the HE-SIG-B content channel 1 is transmitted throughthe P20 channel and the channel through which the HE-SIG-B contentchannel 2 is transmitted may vary. However, depending on the physicalfrequency order of the P20 channel within the P40 channel, the HE-SIG-Bcontent channel 2 may be transmitted through the P20 channel. In thiscase, the channel through which the HE-SIG-B content channel 1 istransmitted may vary depending on the channel configuration. Thenon-contiguous channel allocation information according to theembodiment of the present invention may support at least someconfigurations among the channel configurations listed in FIG. 33 .

FIG. 33(a) illustrates a channel configuration in which only the P20channel is allocated among the P80 (i.e., primary 80 MHz) band. In thiscase, the HE-SIG-B content channel 2 is not transmitted in the P80 band.FIG. 33(b) illustrates a channel configuration in which the P40 channelis basically allocated among the P80 band. In this case, both theHE-SIG-B content channel 1 and the HE-SIG-B content channel 2 may betransmitted through at least the P40 channel According to theembodiment, a non-contiguous channel in which any one among the two 20MHz channels, that is, the S40A channel and the S40B channel of the S40channel is allocated may be used. When both the S40A channel and theS40B channel are allocated, a contiguous channel of 80 MHz or 160 MHzbandwidth is configured.

FIG. 33(c) illustrates a channel configuration in which only the P20channel and the S40A channel are allocated among the P80 band. Accordingto an embodiment, the HE-SIG-B content channel 1 may be transmittedthrough the P20 channel and the HE-SIG-B content channel 2 may betransmitted through the S40A channel. The S40A channel is originally achannel through which the HE-SIG-B content channel 1 is transmitted.However, if there is no other channel through which the HE-SIG-B contentchannel 2 is to be transmitted in the P80 band configuration of thenon-contiguous PPDU, the HE-SIG-B content channel 2 may be transmittedthrough the S40A channel. However, since the change of the HE-SIG-Bcontent channel increases the burden of the PPDU configuration, thechannel configuration of FIG. 33(c) may not be used depending on theembodiment.

FIG. 33(d) illustrates a channel configuration in which only the P20channel and the S40 channel are allocated among the P80 band. In thiscase, the HE-SIG-B content channel 1 may be transmitted through the P20channel and the S40A channel, and the HE-SIG-B content channel 2 may betransmitted through the S40B channel. In addition, FIG. 33(e)illustrates a channel configuration in which only the P20 channel andthe S40B channel are allocated among the P80 band. In this case, theHE-SIG-B content channel 1 may be transmitted through the P20 channel,and the HE-SIG-B content channel 2 may be transmitted through the S40Bchannel. In the embodiments of FIGS. 33(d) and 33(e), the HE-SIG-Bcontent channel 1 and the HE-SIG-B content channel 2 may be transmittedbased on the HE-SIG-B content channel transmission rule according to theembodiment of the present invention

Meanwhile, due to the limitation of the number of bits in the bandwidthfield of the HE-SIG-A, the bandwidth field may indicate someconfigurations among the above channel configurations. When thebandwidth field consists of 3 bits, the bandwidth field may index fouradditional non-contiguous channel allocation information. According tothe embodiment of the present invention, the bandwidth field mayindicate the total bandwidth information through which the PPDU istransmitted and some channel information to be punctured within thetotal bandwidth. In this case, the total bandwidth may be either 80 MHzbandwidth or 160 MHz (or 80+80 MHz) bandwidth. According to anembodiment of the present invention, the bandwidth field may indexpuncturing of the S20 channel shown in FIG. 33(d), and puncturing of atleast one of two 20 MHz channels in the S40 channel shown in FIG. 33(b),respectively.

According to the embodiment of the present invention, in the channelconfiguration indicated by the bandwidth field of the HE-SIG-A,additional puncturing information may be indicated via the RA field ofthe HE-SIG-B. For example, when the bandwidth field indicates puncturingof one of two 20 MHz channels in the S40 channel at the total bandwidthof 80 MHz (e.g., the third and fifth channel configuration in FIG.33(b)), the resource unit allocation field may indicate which 20 MHzchannel in the S40 channel is punctured. Also, when the bandwidth fieldindicates puncturing of at least one of two 20 MHz channels in the S40channel at the total bandwidth of 160 MHz or 80+80 MHz (e.g., thesecond, fourth and sixth channel configurations in FIG. 33(b)), theresource unit allocation field may indicate which 20 MHz channel in theS40 channel is punctured. In addition, when the bandwidth fieldindicates puncturing of at least one of two 20 MHz channels in the S40channel in a total bandwidth of 160 MHz or 80+80 MHz (e.g., the second,fourth and sixth channel configurations in FIG. 33(b)), the resourceunit allocation field may indicate additional puncturing in the S80channel. Further, when the bandwidth field indicates puncturing of theS20 channel in the total bandwidth of 160 MHz or 80+80 MHz (e.g., thesecond channel configuration in FIG. 33(d)), the resource unitallocation field may indicate additional puncturing in the S80 channel.

Channels in which puncturing is indicated as described above are notassigned to the user. A terminal receiving the non-contiguous PPDU mayobtain the total bandwidth information through which the PPDU istransmitted and the channel information to be punctured within the totalbandwidth via the bandwidth field of the HE-SIG-A of the correspondingPPDU. Further, the terminal may obtain additional channel puncturinginformation via the RA field of the HE-SIG-B of the corresponding PPDU.The terminal decodes the PPDU based on the obtained non-contiguouschannel allocation information.

FIG. 34 illustrates a non-contiguous channel allocation method accordingto yet another embodiment of the present invention. Also in theembodiment of FIG. 34 , the location where at least one of the HE-SIG-Bcontent channels is transmitted may be variable. In this case, thereceiver should be able to variably set the decoding channel forreceiving the HE-SIG-B content channel. In the embodiment of FIG. 34 ,it is assumed that the HE-SIG-B content channel 1 is transmitted throughthe P20 channel and the channel through which the HE-SIG-B contentchannel 2 is transmitted may vary.

According to the embodiment of FIG. 34 , the bandwidth field of theHE-SIG-A indicates location information X of the HE-SIG-B contentchannel and size information Y of the common block field of theHE-SIG-B. FIG. 34 illustrates a combination of (X, Y) that can beindicated by the bandwidth field.

First, the location information X of the HE-SIG-B content channel mayindicate a channel through which the HE-SIG-B content channel 2 istransmitted within the P80 channel. When the location informationconsists of 2 bits, it may indicate a total of four channels, that is,P20, S20, S40A and S40B. When the location information consists of 1bit, it may indicate a total of two channels, that is, S20 and S40B. Inthe latter case, even when only the P20 channel is assigned to a user,it can be signaled that the HE-SIG-B content channel is transmittedthrough the S20 channel. However, since no signal is actuallytransmitted through the S20 channel and the receiver would fail todecode the HE-SIG-B content channel on the S20 channel, there is noproblem in a PPDU transmission configured only on the P20 channel.

Next, the size information Y of the common block field may be differentdepending on the number of RA fields to be carried. When the sizeinformation consists of 2 bits, the number of RA fields included in thecommon block field may be indicated as one, two, three, or four. Whenthe size information consists of 1 bit, the number of RA fields includedin the common block field may be indicated as 2 or 4. In the lattercase, an unnecessary RA field may be additionally transmitted. However,it is possible to prevent additional signaling overhead by causing theunnecessary RA field to indicate the unassigned RU described in theembodiment of FIG. 27 .

The receiver may determine a channel to receive the HE-SIG-B contentchannel based on the location information X of the HE-SIG-B contentchannel. In addition, the receiver decodes the common block field of theHE-SIG-B based on the size information of the common block field. Theadditional unassigned channel information of the transmitted PPDU may beindicated via the RA field of the common block field. According to anembodiment of the present invention, a resource unit indication fieldrepresenting which channel each of a plurality of RA fields indicateswithin a bandwidth up to 160 MHz may be used. In this case, the resourceunit indication field may indicate, via a bitmap representing eight 20MHz channels in a bandwidth up to 160 MHz, channels in which thesubsequent RA fields sequentially indicate information.

FIGS. 35 to 37 illustrate embodiments of a resource unit filteringaccording to additional embodiments of the present invention. Referringto FIG. 20 , several embodiments for transmitting a non-contiguous PPDUhave been described. FIGS. 35 to 37 illustrate embodiments in whichadditional resource units are filtered in the non-contiguous PPDUtransmission process described above with reference to FIG. 20 . In theembodiment of the present invention, a filtered resource unit (orchannel) may refer to an unassigned resource unit (or channel).

FIG. 35 illustrates a situation in which a terminal equipped with one RFmodule attempts to transmit a PPDU through a bandwidth of 160 MHz but anS40 channel 640 is busy as a result of CCA. The terminal transmits anon-contiguous PPDU through a 140 MHz band including the P40 channel(i.e., P20 channels+S20 channels) and the S80 channel. In this case, thenon-contiguous PPDU is transmitted using a 160 MHz spectral mask 610.Furthermore, in the S40 channel 640 determined to be busy, filtering isperformed and no data is transmitted. However, since a 40 MHz spectralmask is not applied to the signal transmitted through the P40 channel,signals of some resource units adjacent to the boundary of the S40channel may interfere with OBSS signal transmitted through the S40channel.

Therefore, according to the embodiment of the present invention, in thenon-contiguous PPDU transmission situations, the resource unit adjacentto the unassigned S40 channel 640 may be additionally filtered and beset as the unassigned resource unit. Depending on the location of theS40 channel 640 within the entire bandwidth, a maximum of two adjacentresource units, including a center 26-tone RU 650, on either side of theS40 channel 640 may exist. According to the embodiment of the presentinvention, when a 40 MHz bandwidth channel is set to an unassignedchannel, additional filtering may be performed on a resource unitadjacent to that channel, e.g., the center 26-tone RU 650. Moreover, ifthere is a possibility that some resource units in a transmissionchannel (i.e., P20 channel) adjacent to the unassigned S40 channel 640may interfere with OBSS signal in the unassigned S40 channel 640,additional filtering may be performed on the some resource units.Whether to perform such an additional filtering of resource units may bedetermined based on information of a transmission power of atransmitter, the maximum transmission power per frequency band, thestrength of the received OBSS signal, and the like.

According to an embodiment of the present invention, whether to filterthe center 26-tone RU 650 (i.e., to set as an unassigned resource unit)may be determined as below according to a CCA result of the unassignedS40 channel 640. First, if a legacy PPDU using 64 FFT/20 MHz is detectedin the unassigned S40 channel 640, filtering of the center 26-tone RU650 may be performed. Second, if an HE PPDU using 256 FFT/20 MHz isdetected in the unassigned S40 channel 640, whether to filter the center26-tone RU 650 may be determined based on a band occupied by the HEPPDU. When the band occupied by the HE PPDU is more than a predeterminedfrequency interval away from the center 26-tone RU 650, the center26-tone RU 650 may not be filtered. However, when the band occupied bythe HE PPDU is less than the predetermined frequency interval from thecenter 26-tone RU 650, filtering of the center 26-tone RU 650 may beperformed. Third, if a legacy PPDU or HE PPDU is not detected and anarbitrary radio signal is detected in the unassigned S40 channel 640,whether to filter the center 26-tone RU 650 may be determined based on aband occupied by the signal. When the edge of the band occupied by thesignal is more than a predetermined frequency interval away from thecenter 26-tone RU 650, the center 26-tone RU 650 may not be filtered.

Next, FIG. 36 illustrates a situation in which a terminal equipped withone RF module attempts to transmit a PPDU through a bandwidth of 80 MHzbut an S20 channel 642 is busy as a result of CCA. The terminaltransmits a non-contiguous PPDU through a 60 MHz band including the P20channel and the S40 channel. In this case, the non-contiguous PPDU istransmitted using an 80 MHz spectral mask 612. Furthermore, in the S20channel 642 determined to be busy, filtering is performed and no data istransmitted. However, since a 20 MHz spectral mask is not applied to thesignal transmitted through the P20 channel, signals of some resourceunits adjacent to the boundary of the S20 channel may interfere withOBSS signal transmitted through the S20 channel.

Likewise in the embodiment of FIG. 36 , whether to filter the center26-tone RU 652 and/or the adjacent resource units may be determinedaccording to the method described in the embodiment of FIG. 35 .Moreover, if there is a possibility that some resource units in atransmission channel (i.e., P20 channel) adjacent to the unassigned S20channel 642 may interfere with OBSS signal in the unassigned S20 channel642, additional filtering may be performed on the some resource units.According to an embodiment of the present invention, the transmitter mayminimize resource waste by allocating resource units of a narrowbandwidth to a band adjacent to the unassigned channel in thetransmission channel.

Next, FIG. 37 illustrates a situation in which a terminal equipped withtwo RF modules attempts to transmit a PPDU through a bandwidth of 80+80MHz but an S40 channel 644 is busy as a result of CCA. The terminaltransmits a non-contiguous PPDU through the P40 channel (i.e., P20channel+S20 channel) and the S80 channel, respectively, using the two RFmodules. The terminal transmits, by using the first RF module, the PPDUto which a 40 MHz spectral mask 614 is applied through the P40 channel.In addition, the terminal transmits, by using the second RF module, thePPDU to which an 80 MHz spectral mask 616 is applied through the S80channel. Therefore, in the embodiment of FIG. 37 , no additionalfiltering of some resource units included in the transmission channel(i.e., P20 channel) adjacent to the unassigned S40 channel 644 isrequired. However, at least a half of a center 26-tone RU 654 adjacentto the unassigned S40 channel 644 should be filtered. Thus, according tothe embodiment of the present invention, the center 26-tone RU 654 maybe set as an unassigned resource unit.

FIGS. 38 to 42 illustrate methods of signaling an HE MU PPDU accordingto additional embodiments of the present invention. In the embodimentsof FIGS. 38 to 42 , channel A to channel D refer to respective 20 MHzchannels through which an 80 MHz PPDU is transmitted. In this case, itis designated that channel A is a P20 channel, channel B is an S20channel, and channel C and channel D are an S40 channel. In addition,HE-SIG-B content channel 1 is transmitted through at least one ofchannel A and channel C, and HE-SIG-B content channel 2 is transmittedthrough at least one of channel B and channel D.

FIG. 38 illustrates an embodiment of a method of signaling allocationinformation of a center 26-tone RU in an HE MU PPDU. FIG. 38(a)illustrates resource units constituting a PPDU in a total bandwidth of80 MHz, and FIG. 38(b) illustrates a configuration of HE-SIG-B contentchannel 1 and HE-SIG-B content channel 2 carried via the PPDU. Thespecific method in which the RA field and the user field are carried ineach HE-SIG-B content channel is as described in the previousembodiments.

When a PPDU is transmitted in a total bandwidth of 80 MHz or more, acenter 26-tone RU 502 as shown in FIG. 38(a) may additionally be used.As described above, the common block field of the HE-SIG-B may furtherinclude a C26 field (not illustrated) indicating whether a user isallocated to the center 26-tone RU 502. The C26 field may consist of a1-bit indicator located before or after the RA field in the common blockfield. According to the embodiment of the present invention, the C26field may be carried in both the HE-SIG-B content channel 1 and theHE-SIG-B content channel 2. When the C26 field indicates assignment ofthe center 26-tone RU 502, a user field 422 corresponding to the center26-tone RU 502 should be carried in the HE-SIG-B.

When a PPDU is transmitted in a total bandwidth of 80 MHz, both of a C26field carried in the HE-SIG-B content channel 1 and a C26 field carriedin the HE-SIG-B content channel 2 indicate whether a user is allocatedto the center 26-tone RU 502 in the total bandwidth of 80 MHz. In thiscase, when the C26 field indicates the assignment of the center 26-toneRU 502, the user field 422 corresponding to the center 26-tone RU 502may be carried in the user specific field of the HE-SIG-B contentchannel 1. However, when the C26 field indicates non-assignment of thecenter 26-tone RU 502, the user field 422 corresponding to the center26-tone RU 502 is not carried.

On the other hand, when a PPDU is transmitted in a total bandwidth of160 MHz or 80+80 MHz, the total bandwidth may consist of the first 80MHz bandwidth and the second 80 MHz bandwidth. In this case, the first80 MHz bandwidth may be a frequency band lower than the second 80 MHzbandwidth. A center 26-tone RU may be present in each 80 MHz bandwidth.In this case, the first C26 field carried in the HE-SIG-B contentchannel 1 may indicate whether a user is allocated to the first center26-tone RU of the first 80 MHz bandwidth. In addition, the second C26field carried in HE-SIG-B content channel 2 may indicate whether a useris allocated to the second center 26-tone RU of the second 80 MHzbandwidth. When the first C26 field indicates the assignment of thefirst center 26-tone RU, a user field corresponding to the first center26-tone RU may be carried in the user specific field of the HE-SIG-Bcontent channel 1. Also, when the second C26 field indicates theassignment of the second center 26-tone RU, a user field correspondingto the second center 26-tone RU may be carried in the user specificfield of the HE-SIG-B content channel 2. However, when the first C26field and/or the second C26 field indicate non-assignment of the center26-tone RU, the corresponding user field is not carried.

FIG. 39 illustrates a method of signaling HE-SIG-B in an HE MU PPDUtransmitted through a full bandwidth MU-MIMO. When the full bandwidthMU-MIMO transmission is performed as shown in FIG. 39(a), the RA fieldof the HE-SIG-B need not be transmitted. Thus, the SIG-B compressionfield of the HE-SIG-A may indicate the compression mode of the HE-SIG-Bfield. Meanwhile, the user fields are carried as split to the HE-SIG-Bcontent channel 1 and the HE-SIG-B content channel 2. The receiverdecodes both the HE-SIG-B content channel 1 and the HE-SIG-B contentchannel 2 to identify whether the user field corresponding to thecorresponding terminal is transmitted.

FIG. 39(b) illustrates an embodiment in which a specific subfield of theHE-SIG-A indicates information on the number of MU-MIMO users when afull bandwidth MU-MIMO transmission is performed (i.e., the SIG-Bcompression field indicates the compression mode of the HE-SIG-B field).According to an embodiment of the present invention, when the fullbandwidth MU-MIMO transmission is performed, the SIG-B dual MCS field ofthe HE-SIG-A may indicate information on the number of MU-MIMO users. Itis because the HE-SIG-B content channel 1 and the HE-SIG-B contentchannel 2 do not need to distribute the amount of information throughdifferent MCSs when the full bandwidth MU-MIMO transmission isperformed. According to another embodiment of the present invention,when the full bandwidth MU-MIMO transmission is performed, the number ofHE-SIG-B symbols field in the HE-SIG-A may indicate information on thenumber of MU-MIMO user. It is because, when full-bandwidth MU-MIMOtransmission is performed, it is easier to transmit the information onthe number of MU-MIMO users and the MCS information than to transmit thenumber of HE-SIG-B symbols and MCS information for the decoding of thereceiver.

FIG. 39(c) illustrates the detailed configuration of the HE-SIG-Bcontent channel 1 and the HE-SIG-B content channel 2 when the fullbandwidth MU-MIMO transmission is performed. When the full-bandwidthMU-MIMO is performed, the RA field is not present in the HE-SIG-B.Therefore, when an MU-MIMO transmission is performed through a bandwidthgreater than 20 MHz, the number of users to be allocated to the HE-SIG-Bcontent channel 1 and the HE-SIG-B content channel 2, respectively,should be separately determined.

According to the embodiment of the present invention, when the MU-MIMOtransmission is performed through a bandwidth greater than 20 MHz, userfields may be split equitably between the two content channels for loadbalancing. That is, the number of user fields transmitted in each SIG-Bcontent channel is determined as a round up or down value of a half thetotal number of users. For example, when the total number of user fieldsis n, the first to m-th (where m is ceil (n/2)) user fields may betransmitted through the HE-SIG-B content channel 1, and the m+1-th tothe n-th user fields may be transmitted through the HE-SIG-B contentchannel 2. If n is an odd number, the number of user fields included inthe HE-SIG-B content channel 1 may be one more than the number of userfields included in the HE-SIG-B content channel 2. A total of n userfields are allocated in order of each user field of the HE-SIG-B contentchannel 1, and then each user field of the HE-SIG-B content channel 2.

FIG. 40 illustrates an embodiment of signaling a non-assignment of aspecific resource unit in a non-contiguous PPDU. As described in theembodiments of FIGS. 35 to 37 , in the non-contiguous PPDU transmissionprocess, additional filtering may be performed on some resource units506 of the transmission channel adjacent to the unassigned channelReferring to FIG. 40(a), additional filtering may be performed on theresource unit 506 of the transmission channel (i.e., channel A) adjacentto the unassigned channel, that is, channel B.

FIG. 40(b) illustrates a configuration of the HE-SIG-B indicating thenon-assignment of the specific resource unit 506 in a non-contiguousPPDU. Referring to FIG. 40(b), the RA field of the HE-SIG-B indicatesresource unit allocation information of the transmission channel (i.e.,channel A). Each resource unit of channel A is assigned to STA A1 to STAAn. A user specific field of the HE-SIG-B carries a user fieldcorresponding to each resource unit. In this case, a null STA ID may becontained in a user field 426 corresponding to the resource unit 506 tobe filtered. The specific embodiment of the null STA ID is as describedabove in the embodiments of the previous figures.

FIG. 41 illustrates another embodiment of signaling allocationinformation of the center 26-tone RU 502 in a non-contiguous PPDU. Asdescribed above, the RA field may indicate a specific channel that isnot assigned to a user through a predetermined index. That is, the RAfield may indicate nulling of a bandwidth of a multiple of a 20 MHzchannel, i.e., 242-tone, 484-tone or 996-tone resource unit. As above,when the bandwidth information of the unassigned channel is indicatedvia the RA field, whether the center 26-tone RU 502 is assigned may beimplicitly identified.

First, FIG. 41(a) illustrates a situation in which the S40A channel(i.e., channel C) is busy in a total bandwidth of 80 MHz. The terminaltransmits a PPDU in a 60 MHz band including the P40 channel and the S40Bchannel (i.e., channel D). In this case, the RA field corresponding tochannel C indicates nulling of 242-tone RU. FIG. 41(b) illustrates aconfiguration of the HE-SIG-B content channel 1 and the HE-SIG-B contentchannel 2 of the PPDU transmitted according to the embodiment of FIG.41(a). Since the nulling of 242-tone RU is indicated by the RA field ofthe HE-SIG-B content channel 1, the receiver may identify that a usercan be allocated to the center 26-tone RU 502. Thus, the HE-SIG-Bcontent channel 1 carries a user field 422 corresponding to the center26-tone RU 502.

On the other hand, FIG. 41(c) illustrates a situation in which the S40channel is busy in the total bandwidth of 80 MHz. The terminal transmitsa PPDU through the P40 channel. In this case, the RA fieldscorresponding to channel C and channel D indicate nulling of 484-toneRU. FIG. 41(d) illustrates a configuration of the HE-SIG-B contentchannel 1 and the HE-SIG-B content channel 2 of the PPDU transmittedaccording to the embodiment of FIG. 41(c). Since the nulling of 484-toneRU is indicated by the RA fields of the HE-SIG-B content channel 1 andthe HE-SIG-B content channel 2, the receiver may identify that thecenter 26-tone RU 502 is not assigned to a user. That is, since theentire S40 channel is not assigned to a user, the center 26-tone RU 502may also be set as an unassigned resource unit. Thus, the HE-SIG-Bcontent channel 1 may not carry the user field 422 corresponding to thecenter 26-tone RU 502.

FIG. 42 illustrates a method of transmitting a preamble and data when anon-contiguous PPDU is transmitted according to the embodiment of thepresent invention. In each embodiment of FIGS. 42(a) to 42(c), it isassumed that the S40B channel (i.e., channel D) is busy in the totalbandwidth of 80 MHz. The terminal transmits a PPDU in a 60 MHz bandincluding the P40 channel and the S40A channel (i.e., channel C).

First, according to the embodiment of FIG. 42(a), when transmitting thenon-contiguous PPDU, the terminal may not transmit the preamble inaddition to the data through the unassigned channel. In this case, theterminal does not transmit both the legacy preamble and the non-legacypreamble through the unassigned channel. In such a case, there is anadvantage that no interference may occur to OBSS signal alreadytransmitted through the corresponding channel. In addition, if atransmission is not performed through a specific channel, the dispersionamount of the transmission power is reduced in spite of the transmissionof the wideband PPDU, and the reception ratio of the PPDU is increased.However, this method has a disadvantage in that the signaling of theHE-SIG-B becomes complicated when the S20 channel is busy. In addition,while the HE-STF has a repetitive pattern on the time axis when the PPDUis transmitted through a total bandwidth of 80 MHz, it is difficult tohave a repetitive pattern on the time axis when the HE-STF is nottransmitted on some channels.

Therefore, according to the embodiment of FIG. 42(b), when transmittinga non-contiguous PPDU, the terminal may not transmit data but maytransmit the preamble through the unassigned channel. In this case, theterminal may transmit both the legacy preamble and the non-legacypreamble through the unassigned channel. In such a case, an interferencemay occur to OBSS signal already transmitted through the correspondingchannel. However, since the transmission power may be dispersed to theentire band in the case of the wideband PPDU transmission, there may beno significant damage to the OBSS signal.

According to yet another embodiment of the present invention, theterminal may transmit only HE-STF and HE-LTF (or only HE-STF) throughthe unassigned channel as shown in FIG. 42(c). That is, a transmissionof the legacy preamble, the HE-SIG-A and the HE-SIG-B, of whichreception through the entire band is not required, may be restricted andonly a transmission of the HE-STF and the HE-LTF, of which receptionthrough the entire band is required, may be performed, therebyminimizing interference to the OBSS signal.

FIGS. 43 to 44 illustrate embodiments in which a transmission using anHE MU PPDU is performed between a single STA and an AP. As describedabove, the HE MU PPDU may be used not only for a DL-MU transmission butalso for an uplink transmission.

FIG. 43 illustrates an embodiment in which an HE MU PPDU is used in anuplink transmission of a single STA. According to the embodiment of thepresent invention, a STA may perform a transmission using a resourceunit of 20 MHz bandwidth or less (i.e., a narrowband) as shown in FIG.43(a). The STA may increase a transmission distance of data byconcentrating the transmission power on a specific resource unit. FIGS.43(b) to 43(d) illustrate embodiments for signaling such a narrowbandtransmission.

According to an embodiment of the present invention, the narrowbandtransmission may be signaled via a null STA ID contained in a user fieldof the HE-SIG-B, as shown in FIG. 43(b). More specifically, the RA fieldof the HE-SIG-A may indicate information on resource unit partition typein a specific channel. For example, if a bandwidth of 20 MHz ispartitioned into nine resource units based on OFDMA, the RA field maysignal “00000000” as shown in FIG. 15(c). In this case, an AID of areceiver or a transmitter may be contained in a user field correspondingto a resource unit used for an uplink data transmission among the ninepartitioned resource units. On the other hand, a null STA ID may becontained in user fields corresponding to the remaining resource unitsthrough which data transmission is not performed.

For example, when data is transmitted only through the third 26-tone RUamong the nine resource units, a null STA ID may be contained in thefirst to second user fields and the fourth to ninth user fields.However, if the signaling structure of the HE-SIG-B, which is designedbased on the DL-MU transmission, is directly used in the uplinknarrowband transmission, the signaling overhead may be increased. Thus,other signaling methods may be used to reduce the signaling overhead.According to another embodiment of the present invention, user fieldsafter a user field in which the AID of the receiver or transmitter iscontained may be excluded from the signaling. That is, in the aboveembodiment, the null STA ID is contained in the first to second userfields, and the AID of the receiver or transmitter may be contained inthe third user field. However, the fourth to ninth user fields may notbe transmitted. It is because the AP receiving the PPDU does not need toreceive additional user fields after obtaining information of thetransmitting STA in the third user field.

According to another embodiment of the present invention, index valuesfor the uplink resource unit allocation may be newly defined in the RAfield of the HE-SIG-B for the narrowband transmission as shown in FIG.43(c). More specifically, the RA field of the HE-SIG-B may index aspecific 26-tone RU, 52-tone RU and/or 106-tone RU through which anuplink transmission is performed. In this case, since only one userfield corresponding to a resource unit indicated by the RA field iscarried, the signaling overhead may be greatly reduced. According to anembodiment, index values for the uplink resource unit allocation may beused among unassigned (i.e., TBD) indices of the RA field configurationfor the DL-MU transmission. According to another embodiment, the indexvalues for the uplink resource unit allocation may be newly defined inthe RA field.

According to yet another embodiment of the present invention, thenarrowband transmission may be signaled by recycling unnecessary fieldsof the HE-SIG-A. For example, if the HE MU PPDU is used in the uplinktransmission, the number of HE-LTF symbols field and the number ofHE-SIG-B symbols field in the HE-SIG-A may be used for other purposes.Since the number of HE-LTF symbols field has a function redundant withthe NSTS field of the user specific field of the HE-SIG-B, no separatesignaling is required. Also, in a signaling of a single STA, since theamount of signaling information is fixed and the number of symbols canbe fixed according to the design, it is not necessary to indicate thenumber of symbols separately through the number of HE-SIG-B symbolsfield. Accordingly, it is possible to perform signaling of the uplink HEMU PPDU using at least one of the above fields. For example, in theresource unit allocation indicated by the RA field, the location of theresource unit through which the STA transmits the uplink data may beindicated using at least one of the above fields. In this case, the RAfield of the HE-SIG-B is set to be the same as the conventional one, andthe signaling overhead can be reduced since only one user field iscarried.

Meanwhile, according to still another embodiment of the presentinvention, the uplink transmission using the HE MU PPDU may be performednot only through the narrowband but also through the entire bandwidth of20 MHz, 40 MHz, 80 MHz, or 160 MHz (80+80 MHz). In this case, thebandwidth field of the HE-SIG-A may indicate the total bandwidth of thePPDU, and the SIG-B compression field may indicate the compression modeof the HE-SIG-B field. Therefore, the RA field of the HE-SIG-B may beomitted in an uplink HE MU PPDU. On the other hand, when the SIG-Bcompression field indicates the compression mode of the HE-SIG-B fieldin a downlink HE MU PPDU, MU-MIMO based user specific information couldbe indicated. However, when the SIG-B compression field indicates thecompression mode of the HE-SIG-B field in an uplink HE MU PPDU,OFDMA-based user specific information may be indicated as shown in FIG.43(c).

FIG. 44 illustrates a method of configuring the HE-SIG-B when a singleSTA transmits a non-contiguous PPDU to an AP. In the embodiment of FIG.44 , the S20 channel is busy in a total bandwidth of 80 MHz. Therefore,the STA transmits a PPDU in a 60 MHz band including the P20 channel andthe S40 channel.

The bandwidth field of the HE-SIG-A defined in the existing HE SU PPDUformat is not suitable for signaling a non-contiguous PPDU. Therefore,the STA may perform the transmission of the non-contiguous PPDU usingthe HE MU PPDU format. In this case, the bandwidth field of the HE-SIG-Aindicates puncturing of the S20 channel in the total bandwidth of 80MHz. The HE-SIG-B carries information of the single STA (i.e., SU Info)through the P20 channel and the S40 channel.

Meanwhile, since the configuration information of the non-contiguousPPDU is signaled via the bandwidth field, the common block field of theHE-SIG-B may be omitted. Therefore, the SIG-B compression field mayindicate the compression mode of the HE-SIG-B field. In addition, theuser specific field of the HE-SIG-B may carry only one user field. Inthis case, an AID of a transmitter, not an AID of a receiver, iscontained in the user field. When the HE MU PPDU is used for the uplinktransmission, it is obvious that the receiver of the corresponding PPDUis an AP. When the UL/DL field of the HE MU PPDU indicates an uplinktransmission, the AP may interpret the AID contained in the user fieldas the AID of the transmitter.

FIGS. 45 to 46 illustrate methods of a non-contiguous channel allocationand a signaling thereof according to additional embodiments of thepresent invention. As described above, according to an embodiment of thepresent invention, a wideband PPDU may be transmitted according to anon-contiguous, limited flexible channel extension method.

FIG. 45 illustrates a method of signaling the HE-SIG-A and the HE-SIG-Bwhen a PPDU is transmitted according to a non-contiguous, limitedflexible channel extension method. As described above with reference toFIG. 19(e), the flexible channel extension method refers to a channelextension method in which a band occupied by a transmitted PPDU alwaysincludes predetermined core channels including the P20 channel. In theembodiment of FIG. 45 , the P40 channel including the P20 channel andthe S20 channel is set as the core channels. However, the core channelsare selected bandwidths to reduce the signaling burden of the HE-SIG-B,and if the signaling burden of the HE-SIG-B is not increased, the corechannels can be changed according to the embodiment.

First, FIG. 45(a) illustrates a situation in which the S40B channel andthe S80 channel are busy in a total bandwidth of 160 MHz. The terminaltransmits a non-contiguous PPDU through a 60 MHz band including the P40channel and the S40A channel. In this case, the bandwidth field of theHE-SIG-A of the transmitted PPDU may indicate 160 MHz. The HE-SIG-Bcontent channel 1 carries allocation information of channel A andchannel C (i.e., A, C, 996-null, 996-null) and is transmitted throughchannel A and channel C. The HE-SIG-B content channel 2 carriesallocation information of CH B (i.e., B, 242-Null, 996-null, 996-null)and is transmitted through channel B.

Next, FIG. 45(b) illustrates a situation in which the S40A channel andthe S80 channel are busy in a total bandwidth of 160 MHz. The terminaltransmits a non-contiguous PPDU through a 60 MHz band including the P40channel and the S40B channel. In this case, the bandwidth field of theHE-SIG-A of the transmitted PPDU may indicate 160 MHz. The HE-SIG-Bcontent channel 1 carries allocation information of channel A (i.e., A,242-Null, 996-null, 996-null) and is transmitted through channel A.HE-SIG-B content channel 2 carries allocation information of channel Band channel D (i.e., B, D, 996-null, 996-null) and is transmittedthrough channel B and channel D.

Next, FIG. 45(c) illustrates a situation in which a PPDU is transmittedonly through the P20 channel in a total bandwidth of 160 MHz. In thiscase, the bandwidth field of the HE-SIG-A of the transmitted PPDUindicates 160 MHz, and the HE-SIG-B content channel 1 carries allocationinformation of channel A (i.e., A, 242-Null, 996-null, 996-null). Inthis case, since the signaling burden of the HE-SIG-B is not increased,it is possible to transmit a PPDU not occupying at least a part of thecore channels.

Finally, FIG. 45(d) illustrates a situation in which the S40B channel,the S80A channel, the S80C channel and the S80D channel are busy in atotal bandwidth of 160 MHz. The terminal transmits a non-contiguous PPDUthrough an 80 MHz band including the P40 channel, the S40A channel, andthe S80B channel. In this case, the bandwidth field of the HE-SIG-A ofthe transmitted PPDU may indicate 160 MHz. The HE-SIG-B content channel1 carries allocation information of channel A and channel C (i.e., A, C,242-null, 484-null) and is transmitted through channel A and channel C.The HE-SIG-B content channel 2 carries allocation information of channelB and channel F (i.e., B, 242-Null, F, 484-Null) and is transmittedthrough channel B and channel F.

In the channel allocation information (i.e., A1, A2, A3 and A4)described with reference to the respective drawings, the A1, A2, A3 andA4 denote the first RA field, the second RA field, the third RA fieldand the fourth RA field which are carried in the HE-SIG-B contentchannel, respectively. As above, according to the embodiment of thepresent invention, various non-contiguous PPDUs may be signaled via acombination of the HE-SIG-A and the HE-SIG-B.

FIG. 46 illustrates a channel allocation method when a PPDU istransmitted according to a non-contiguous, limited flexible channelextension method. FIG. 46(a) illustrates options of non-contiguouschannel allocation in a total bandwidth of 80 MHz, and FIG. 46(b)illustrates options of non-contiguous channel allocation in a totalbandwidth of 160 MHz. In FIG. 46(b), the P80 channel may consist of anyone of the channels shown in FIG. 46(a).

The non-assignment information of the S80 channel shown in FIG. 46(b)may be indicated via the RA field of the HE-SIG-B or indicated by thenull STA ID of the user field, as described above. In addition, whetherthe center 26-tone RU shown in FIGS. 46(a) and 46(b) is assigned may beindicated via the C26 field of the HE-SIG-B.

Although the present invention is described by using the wireless LANcommunication as an example, the present invention is not limitedthereto and the present invention may be similarly applied even to othercommunication systems such as cellular communication, and the like.Further, the method, the apparatus, and the system of the presentinvention are described in association with the specific embodiments,but some or all of the components and operations of the presentinvention may be implemented by using a computer system having universalhardware architecture.

The detailed described embodiments of the present invention may beimplemented by various means. For example, the embodiments of thepresent invention may be implemented by a hardware, a firmware, asoftware, or a combination thereof.

In case of the hardware implementation, the method according to theembodiments of the present invention may be implemented by one or moreof Application Specific Integrated Circuits (ASICSs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, micro-controllers, micro-processors,and the like.

In case of the firmware implementation or the software implementation,the method according to the embodiments of the present invention may beimplemented by a module, a procedure, a function, or the like whichperforms the operations described above. Software codes may be stored ina memory and operated by a processor. The processor may be equipped withthe memory internally or externally and the memory may exchange datawith the processor by various publicly known means.

The description of the present invention is used for exemplification andthose skilled in the art will be able to understand that the presentinvention can be easily modified to other detailed forms withoutchanging the technical idea or an essential feature thereof. Thus, it isto be appreciated that the embodiments described above are intended tobe illustrative in every sense, and not restrictive. For example, eachcomponent described as a single type may be implemented to bedistributed and similarly, components described to be distributed mayalso be implemented in an associated form.

The scope of the present invention is represented by the claims to bedescribed below rather than the detailed description, and it is to beinterpreted that the meaning and scope of the claims and all the changesor modified forms derived from the equivalents thereof come within thescope of the present invention.

INDUSTRIAL APPLICABILITY

Various exemplary embodiments of the present invention have beendescribed with reference to an IEEE 802.11 system, but the presentinvention is not limited thereto and the present invention can beapplied to various types of mobile communication apparatus, mobilecommunication system, and the like.

1-18. (canceled)
 19. A wireless communication terminal, the terminalcomprising: a processor; and a communication unit, wherein the processoris configured to: receive a preamble of a wireless packet including aHigh Efficiency Signal A (HE-SIG-A) field and a High Efficiency Signal B(HE-SIG-B) field through the communication unit, wherein the HE-SIG Afield includes a bandwidth subfield, wherein the HE-SIG B field consistsof a first at least one HE-SIG-B content channel and a second at leastone HE-SIG B content channel, and wherein the preamble further includesa C26 subfield indicating whether a user is allocated to a center26-tone resource unit of 80 MHz when the wireless packet is transmittedin a total bandwidth of 80 MHz or more, receive a data of the wirelesspacket based on the C26 subfield.
 20. The wireless communicationterminal of claim 19, wherein the first at least one HE-SIG B contentchannel and the second at least one HE-SIG-B content channel aretransmitted separately in units of 20 MHz.
 21. The wirelesscommunication terminal of claim 19, wherein a value of the C26 subfieldis set to the same value for the first at least one HE-SIG-B contentchannel and the second at least one HE-SIG-B content channel.
 22. Thewireless communication terminal of claim 19, wherein the C26 subfieldindicate whether a user is allocated to a center 26-tone resource unitin the total bandwidth of 80 MHz when the wireless packet is transmittedin the total bandwidth of 80 MHz.
 23. The wireless communicationterminal of claim 19, wherein a user field corresponding to the center26-tone resource unit is carried in a user specific field of each of thefirst at least one HE-SIG-B content channel and the second at least oneHE-SIG-B content channel when the C26 subfield indicates that a user isallocated to the center 26-tone resource unit.
 24. The wirelesscommunication terminal of claim 19, wherein the total bandwidth includesa first 80 MHz bandwidth and a second 80 MHz bandwidth when the wirelesspacket is transmitted in a total bandwidth of 160 MHz bandwidth, whereina first C26 subfield related to the first at least one HE-SIG-B contentchannel indicates whether a user is allocated to a first center 26-toneresource unit in the first 80 MHz bandwidth, and wherein a second C26subfield related to the second at least one HE-SIG-B content channelindicates whether a user is allocated to a second center 26-toneresource unit in the second 80 MHz bandwidth.
 25. The wirelesscommunication terminal of claim 19, wherein each of the first at leastone HE-SIG-B content channel and the second at least one HE-SIG-Bcontent channel includes a subfield related to information of anunassigned resource unit, and wherein the data of the wireless packet isreceived in a resource unit except for the unassigned resource unit. 26.A wireless communication method of a wireless communication terminal,the method comprising: receiving a preamble of a wireless packetincluding a High Efficiency Signal A (HE-SIG-A) field and a HighEfficiency Signal B (HE-SIG-B) field through the communication unit,wherein the HE-SIG-A field includes a bandwidth subfield, wherein theHE-SIG-B field consists of a first at least one HE-SIG-B content channeland a second at least one HE-SIG-B content channel, and wherein thepreamble further includes a C26 subfield indicating whether a user isallocated to a center 26-tone resource unit of 80 MHz when the wirelesspacket is transmitted in a total bandwidth of 80 MHz or more; andreceiving a data of the wireless packet based on the C26 subfield. 27.The wireless communication method of claim 26, wherein the first atleast one HE-SIG-B content channel and the second at least one HE-SIG-Bcontent channel are transmitted separately in units of 20 MHz.
 28. Thewireless communication method of claim 26, wherein a value of the C26subfield is set to the same value for the first at least one HE-SIG-Band the second at least one HE-SIG-B subfield.
 29. The wirelesscommunication method of claim 26, wherein the C26 subfield indicatewhether a user is allocated to a center 26-tone resource unit in thetotal bandwidth of 80 MHz when the wireless packet is transmitted in thetotal bandwidth of 80 MHz.
 30. The wireless communication method ofclaim 26, wherein a user field corresponding to the center 26-toneresource unit is carried in a user specific field of each of the firstat least one HE-SIG-B content channel and the second at least oneHE-SIG-B content channel when the C26 subfield indicates that a user isallocated to the center 26-tone resource unit.
 31. The wirelesscommunication method of claim 26, wherein the total bandwidth includes afirst 80 MHz bandwidth and a second 80 MHz bandwidth when the wirelesspacket is transmitted in a total bandwidth of 160 MHz bandwidth, whereina first C26 subfield related to the first at least one HE-SIG-B contentchannel indicates whether a user is allocated to a first center 26-toneresource unit in the first 80 MHz bandwidth, and wherein a second C26subfield related to the second at least one HE-SIG-B content channelindicates whether a user is allocated to a second center 26-toneresource unit in the second 80 MHz bandwidth.
 32. The wirelesscommunication method of claim 26, wherein each of the first at least oneHE-SIG-B content channel and the second at least one HE-SIG-B contentchannel includes a subfield related to information of an unassignedresource unit, and wherein the data of the wireless packet is receivedin a resource unit except for the unassigned resource unit.